EXECUTION

     

    

      EXCHANGE
        TRUST AGREEMENT

       

      This
        EXCHANGE TRUST AGREEMENT (this “Agreement”)
        dated
        as of November 1, 2007, is executed by and among Structured Asset Securities
        Corporation, as depositor (the “Depositor”),
        U.S.
        Bank National Association, solely in its capacity as trustee pursuant to
        the
        Underlying Trust Agreement (as defined below) (the “Trustee”)
        and
        Wells Fargo Bank, N.A., as securities administrator (the “Securities
        Administrator”).

       

      WITNESSETH

      


      WHEREAS,
        the Depositor, the Trustee, the Securities Administrator and Aurora Loan
        Services, LLC, as Master Servicer have entered into a Trust Agreement (the
        “Underlying
        Trust Agreement”)
        dated
        as of November 1, 2007 establishing Lehman Mortgage Trust 2007-10 (the
“Underlying
        Trust”);

       

      WHEREAS,
        the Underlying Trust has issued a series of certificates known as Mortgage
        Pass-Through Certificates, Series 2007-10, evidencing the entire beneficial
        interest in the Underlying Trust;

       

      WHEREAS,
        the Exchange Classes and Exchangeable Classes (each as defined herein) will
        be
        issued hereunder and will represent ownership interests in the Related REMIC
        Classes (as defined herein);

       

      WHEREAS,
        all or a portion of the Exchange Classes may be exchanged for the related
        Exchangeable Classes and vice versa; and

       

      WHEREAS,
        the parties hereto desire to create this Trust to issue the Exchange Classes
        and
        the Exchangeable Classes subject to the terms and conditions set forth
        herein.

       

      NOW
        THEREFORE, the parties to this Agreement, in the several capacities hereinabove
        set forth, do hereby declare and establish this Agreement and do hereby
        undertake and otherwise agree as follows:

       

      ARTICLE
        I

       

      DEFINED
        TERMS

       

      Capitalized
        terms used and not defined herein shall have the respective meanings assigned
        to
        them in the Underlying Trust Agreement and the rules of construction set
        forth
        therein shall apply hereto. In addition, whenever used in this Agreement,
        the
        following words and phrases, unless the context otherwise requires, shall
        have
        the following meanings:

       

      “Aggregate
        Denomination”:
        As to
        any Class and date of determination, the aggregate of the denominations of
        the
        Outstanding Certificates of such Class on such date.

       

      “Authorized
        Officer”:
        The
        Chairman of the Board, the President or any Executive Vice President, Senior
        Vice President or Vice President.

       


      
        
          
          

        

        
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      “Certificate”:
        A
        grantor trust pass-through security issued hereunder in a book-entry form
        as
        authorized by this Agreement.

       

      “Certificate
        Registrar”:
        For
        the purposes of this Agreement, the Securities Administrator appointed pursuant
        to the Underlying Trust Agreement which shall act as Certificate Registrar
        under
        this Agreement subject to the terms and conditions and entitled to the same
        rights, protections and indemnities set forth in the Agreement.

       

      “Class”:
        Each
        Class of Certificates issued or issuable hereunder as set forth in Section
        2.02
        hereto and each REMIC Class issued under the Underlying Trust
        Agreement.

       

      “Class
        Balance”:
        With
        respect to any Exchangeable Class or Exchange Class, at any time, the aggregate
        of the Certificate Principal Amounts of all Outstanding Certificates of such
        Class.

       

      “Class
        Distribution Amount”:
        As to
        each Exchangeable Class and Exchange Class and any Distribution Date, an
        amount
        equal to the aggregate of the Class Interest Distribution Amount and Class
        Principal Distribution Amount on such date. As to each Related REMIC Class
        on
        any Distribution Date, the sum of (i) the Accrued Certificate Interest
        distributable to such Class pursuant to the Underlying Trust Agreement on
        such
        date; and (ii) the amount of principal distributable to such Class pursuant
        to
        the Underlying Trust Agreement on such date.

       

      “Class
        Interest Distribution Amount”:
        As to
        each Exchangeable Class and Exchange Class, and each Distribution Date, an
        amount equal to Accrued Certificate Interest (as defined in the Underlying
        Trust
        Agreement) for such class.

       

      “Class
        Principal Distribution Amount”:
        As to
        each Exchangeable Class and Exchange Class, and each Distribution Date, an
        amount as to principal equal to (i) the concurrent distribution of principal
        in
        respect of each Related REMIC Class multiplied by (ii) a fraction, the numerator
        of which is the Aggregate Denomination of such Class and the denominator
        of
        which is the Initial Authorized Denomination of such Class.

       

      “Code”:
        The
        Internal Revenue Code of 1986, as amended, including any successor or amendatory
        provisions.

       

      “Combination
        Group”:
        Any
        allowable combination of Certificates as set forth on Appendix A.

      


      “Distribution
        Date”:
        As to
        any Exchangeable Class and Exchange Class, the Distribution Date for the
        Related
        REMIC Classes.

       

      “Exchange
        Classes”
or
        “Exchange
        Certificates”:
        Each
        Class of Certificates identified as such in Appendix A hereto and issued
        hereunder.

       

      “Exchangeable
        Classes”
or
        “Exchangeable
        Certificates”:
        Each
        Class of Certificates identified as such in Appendix A hereto and issued
        hereunder.

       


      
        
          
          

        

        
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      “Initial
        Authorized Denomination”:
        With
        respect to any Class and Combination Group, the amount set forth with respect
        to
        such Class and such Combination Group in Appendix A under the heading “Maximum
        Balance” or “Maximum Original Balance.”

       

      “Issue
        Date”:
        November 30, 2007.

       

      “Notional
        Amount”:
        With
        respect to any Notional Exchange Classes, as set forth in Appendix
        A
        hereto.

       

      “Notional
        Exchange Classes”:
        Not
        applicable.

       

      “Outstanding
        Certificate”:
        Any
        Outstanding Exchange Certificate and Outstanding Exchangeable
        Certificate.

       

      “Outstanding
        Exchangeable Certificate”:
        Any
        Exchangeable Certificate issued on the Issue Date; provided,
        however,
        that
        upon the exchange of any Exchangeable Certificate pursuant to Section 2.03
        hereof, the Exchangeable Certificate so exchanged shall be deemed no longer
        to
        be an Outstanding Certificate, and each Exchange Certificate issued in exchange
        therefor shall be deemed to be an Outstanding Exchange Certificate.

       

      “Outstanding
        Exchange Certificate”:
        Any
        Exchange Certificate issued on the Issue Date; provided,
        however,
        that
        upon the exchange of any Exchange Certificate pursuant to Section 2.03 hereof,
        the Exchange Certificate so exchanged shall be deemed no longer to be an
        Outstanding Exchange Certificate, and the Exchangeable Certificate issued
        in
        exchange therefor shall be deemed to be an Outstanding Exchangeable
        Certificate.

       

      “Paying
        Agent”:
        For
        the purposes of this Agreement, the Securities Administrator appointed pursuant
        to the Underlying Trust Agreement which shall act as Paying Agent under this
        Agreement subject to the same terms and conditions and entitled to the same
        rights, protections and indemnities set forth in the Underlying Trust
        Agreement.

       

      “Prospectus”:
        The
        prospectus dated November 26, 2007, as supplemented by a prospectus supplement
        dated November 28, 2007, relating to the Lehman Mortgage Trust, Mortgage
        Pass-Through Certificates Series 2007-10.

       

      “Realized
        Loss Allocation Amount”:
        As to
        each Exchangeable Class or Exchange Class and Distribution Date, an amount
        equal
        to the aggregate of the Realized Losses on such Distribution Date in respect
        of
        the Related REMIC Class or Classes multiplied by a fraction, the numerator
        of
        which is equal to the Aggregate Denomination of such Exchange or Exchangeable
        Class at the close of business on the related Record Date and the denominator
        of
        which is the Initial Authorized Denomination with respect to such Class.
        

       

      “Related
        REMIC Class”:
        As to
        any Exchange Class (and each Exchangeable Class of the same Combination Group),
        the REMIC Class with the identical class designation as such Exchange
        Class.

       

      “REMIC
        Class”
or
        “REMIC
        Certificates”:
        Each
        of the following Classes of Certificates issued under the Underlying Trust
        Agreement in uncertificated form: the Class
        1-A1, Class 1-A2, Class 2-A2, Class 2-A3, Class 2-A4, Class 2-A9, Class 2-A11,
        Class 2-A12, Class 3-A3, Class 3-A4, Class 3-A5, Class 3-A6, Class 3-A10,
        Class
        3-A12, Class 3-A13, Class 4-A2, Class 4-A3, Class 4-A4, Class AP2 and Class
        AP3
Certificates.

       


      
        
          
          

        

        
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      “Trust”:
        The
        trust created by this Agreement, the corpus of which consists of the Trust
        Fund.

       

      “Trust
        Account”:
        As
        defined in Section 3.02 hereof.

       

      “Trust
        Fund”:
        The
        corpus of the trust created by this Agreement, consisting of the Trust Account
        and the uncertificated interests in the REMIC Certificates issued by the
        Underlying Trust and all payments thereon and all rights
        thereunder.

       

      “Underlying
        Trust”:
        As
        defined in the Preamble hereof.

       

      “WHFIT”:
        A
“widely held fixed investment trust” as that term is defined in Treasury
        Regulations section 1.671-5(b)(22) or successor provisions.

       

      “WHFIT
        Regulations”:
        Treasury Regulations section 1.671-5, as amended.

       

      “WHMT”:
        A
“widely held mortgage trust” as that term is defined in Treasury Regulations
        section 1.671-5(b)(23) or successor provisions.

       

       

      ARTICLE
        II

       

      THE
        TRUST

       

      Section
        2.01. Acceptance
        of REMIC Certificates.
        Wells
        Fargo Bank, N.A., acting as custodian for the Trustee for the benefit of
        the Certificateholders, acknowledges the transfer and assignment to it of
        the
        uncertificated REMIC Certificates and hereby declares that it will hold the
        same
        in trust for the Certificateholders on the terms in this Agreement
        contained.

       

      Section
        2.02. Certificates.
        The
        Certificates authorized by this Agreement shall consist of each Exchange
        Class and Exchangeable Class having the characteristics specified or determined
        as provided in Appendix A and the Underlying Trust Agreement, and otherwise
        shall be subject to the terms and provisions set forth herein. 

       

      Section
        2.03. Exchanges.
        Certificates shall be exchangeable on the books of DTC, on and after the
        Closing
        Date, by notice to the Securities Administrator and under the terms and
        conditions hereinafter set forth.

       

      In
        the
        case of each Combination Group, Exchange Certificates in such Combination
        Group
        shall be exchangeable for Exchangeable Certificates related to such Combination
        Group in respective denominations determined based on the proportion that
        the
        initial Certificate Principal Balances of such Exchange Certificates bear
        to the
        original Certificate Principal Balances of the related Exchangeable
        Certificates, as set forth in Appendix A. Upon any such exchange the portions
        of
        the Exchange Certificates designated for exchange shall be deemed cancelled
        and
        replaced by the Exchangeable Certificates issued in exchange therefor.
        Correspondingly, Exchangeable Certificates related to a Combination Group
        may be
        further designated for exchange for Certificates of the Exchange Classes
        in such
        Combination Group in respective denominations determined based on the proportion
        that the initial Certificate Principal Balances of such Exchangeable
        Certificates bear to the original Certificate Principal Balances of the related
        Exchange Certificates, as set forth in Appendix A. There shall be no limitation
        on the number of exchanges authorized pursuant to this Section 2.03, and,
        except
        as set forth below, no fee or other charge shall be payable to the Trustee,
        the
        Securities Administrator or DTC in connection therewith.


      
        
          
          

        

        
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      Upon
        the
        presentation and surrender by any Holder of its Certificates in the appropriate
        combination as set forth on Appendix A, such Holder shall hereunder transfer,
        assign, set over and otherwise convey to the Trustee, all of such Holder’s
        right, title and interest in and to such Certificates, including all payments
        of
        interest thereon received after the month of the date specified in the notice
        (as described in the immediately succeeding paragraph) relating to such
        exchange.

      


      In
        order
        to effect an exchange of Certificates, the Certificateholder shall provide
        notice to the Securities Administrator (substantially in the form of Exhibit
        I
        hereto) in writing or by e-mail at GCTSSPGTEAMC-1@wellsfargo.com,
        Rebecca.A.Lisi@wellsfargo.com
        and
Scott.Runkles@wellsfargo.com
        no later
        than two Business Days before the proposed exchange date. The exchange date
        may
        be any Business Day from and including the 25th
        day of
        the month to the second to the last Business Day of the month subject to
        the
        Securities Administrator’s approval. The notice must be on the
        Certificateholder’s letterhead, carry a medallion stamp guarantee and set forth
        the following information: the CUSIP number of both Certificates to be exchanged
        and Certificates to be received; outstanding Certificate Balance or Notional
        Amount and the Original Certificate Balance or Notional Amount of the
        Certificates to be exchanged; the Certificateholder’s DTC participant number;
        and the proposed exchange date. After receiving the notice, the Securities
        Administrator shall e-mail the Certificateholder with wire payment instructions
        relating to the exchange fee. A notice becomes irrevocable on the second
        Business Day before the proposed exchange date.

      


      Notwithstanding
        any other provision herein set forth, a fee shall be payable to the Securities
        Administrator in connection with each exchange equal to $5,000 for each exchange
        request.

      


      The
        Securities Administrator shall make the first distribution on an Exchange
        Certificate or an Exchangeable Certificate received in an exchange transaction
        on the Distribution Date in the following month to the Certificateholder
        of
        record as of the close of business on the last day of the month of the
        exchange.

      


      Section
        2.04. Delivery
        of Instruments.
        The
        Securities Administrator shall furnish to each Holder, upon request, copies
        of
        this Agreement, without attachments, applicable to the Certificate(s) held
        by
        such Holder.

       


      
        
          
          

        

        
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      ARTICLE
        III

       

      CERTIFICATES;
        DISTRIBUTIONS

       

      Section
        3.01. Issuance
        of Certificates.
        The
        Classes of Certificates issued hereunder shall be issued in book-entry form
        and
        shall be maintained in the names of the record owners thereof as entries
        on the
        books of DTC. Such Certificates shall be in authorized denominations set
        forth
        herein and in the Underlying Trust Agreement.

       

      Section
        3.02. Trust
        Account.
        On or
        before the Issue Date, the Securities Administrator shall either (i) open
        with a depository institution one or more trust accounts in the name of the
        Trustee on behalf of the Trust Fund that shall collectively be the “Trust
        Account,”
        (ii) in lieu of maintaining any such account or accounts, maintain the
        Trust Account by means of appropriate entries on its books and records
        designating all amounts credited thereto in respect of the REMIC Certificates
        and all investments of any such amounts as being held by it in its capacity
        as
        Securities Administrator for the benefit of the Holders of the Certificates
        or
        (iii) maintain the Trust Account in the form of any combination of accounts
        or book entries described in clauses (i) and (ii) above. Any manner or manners
        in which the Trust Account is maintained may at any time be changed without
        notice to, or the approval of Holders of, the Certificates so long as funds
        held
        in the Trust Fund by, or for the account of, the Securities Administrator
        shall
        at all times be identified. To the extent that the Trust Account is maintained
        by the Securities Administrator in the manner provided for in clause (ii)
        above,
        all references herein to deposits and withdrawals from the Trust Account
        shall
        be deemed to refer to credits and debits to the related books of the Securities
        Administrator.

       

      The
        Securities Administrator shall deposit in the Trust Account all distributions
        in
        respect of the REMIC Certificates received by it as Securities Administrator
        hereunder. All such distributions deposited from time to time in the Trust
        Account and all investments made with such moneys, including all income or
        other
        gain from such investments, shall be held by the Securities Administrator
        in the
        Trust Account as part of the Trust Fund as herein provided, subject to
        withdrawal by the Securities Administrator for distributions on the
        Certificates.

       

      Section
        3.03. Distributions.
        On each
        Distribution Date, the Securities Administrator shall withdraw from the Trust
        Account the Class Distribution Amount for each Class and shall cause the
        Paying
        Agent to make the appropriate distributions to the Holders of each such Class.
        All distributions of such Class Distribution Amount that are made with respect
        to a particular Class shall be made pro
        rata
        among
        all Certificates of such class in proportion to their respective Certificate
        Balances, with no preference or priority of any kind. As among any Outstanding
        Exchange Classes, distributions shall be made to such Certificates, pro
        rata,
        in
        proportion to the Class Principal Balance of each such Class.

       

      Section
        3.04. Allocation
        of Realized Losses.
        On each
        Distribution Date, the Realized Loss Allocation Amount for each Exchange
        and
        Exchangeable Class shall be applied to such Class in reduction of the balances
        thereof.

       


      
        
          
          

        

        
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      ARTICLE
        IV

       

      LIMITATION
        OF LIABILITY

       

      The
        Trustee and the Securities Administrator shall be entitled to the same rights,
        protections and indemnities afforded to them under the Underlying Trust
        Agreement. The Trustee shall not be liable for any act or omission of the
        Securities Administrator under this Agreement.

       

      ARTICLE
        V

       

      THE
        TRUSTEE

       

      In
        the
        event that the Trustee, as holder of the REMIC Certificates, is requested
        to
        vote in respect of any matter arising under the Underlying Trust Agreement
        that
        requires the vote of Holders of Certificates outstanding thereunder, the
        Trustee
        shall vote such REMIC Certificates in such amounts and proportions as shall
        reflect instructions received from Holders of any Outstanding Exchange
        Certificates and Outstanding Exchangeable Certificates: provided, that
        absent receipt of such instructions, the Trustee shall abstain from voting.
        The
        Securities Administrator shall promptly notify the Holders of any outstanding
        Exchange Certificates of any such matter requiring their vote or
        consent.

       

      ARTICLE
        VI

       

      TERMINATION

       

      The
        respective obligations and responsibilities of the Securities Administrator
        and
        the Trustee shall terminate as to the Trust upon the same terms and conditions
        as the Underlying Trust pursuant to the Underlying Trust Agreement.

       

      ARTICLE
        VII

       

      SUPPLEMENTAL
        AGREEMENTS

       

      This
        Agreement may be amended or supplemented from time to time by the Depositor,
        the
        Securities Administrator and the Trustee upon the same terms and conditions
        as
        the Underlying Trust Agreement may be amended or supplemented.

       

      ARTICLE
        VIII

       

      MISCELLANEOUS

       

      Section
        8.01. Certificateholders.
        The
        death of incapacity of any Certificateholder shall neither operate to terminate
        this Agreement, nor entitle such Certificateholder’s legal representative or
        heirs to claim an accounting or to take any action or proceeding in any court
        for a partition or winding-up of the affairs of the Trust Fund, nor otherwise
        affect the rights, duties and obligations of any of the parties to this
        Agreement.

       

      Except
        as
        provided in Article V and Article VII, no Certificateholder shall have any
        right
        to vote or in any manner otherwise control the operation and management of
        the
        Trust Fund or the obligations of the parties hereto, nor shall anything herein
        set forth, or contained in the terms of the Certificates, be construed so
        as to
        constitute the Certificateholders from time to time as partners or members
        of an
        association; nor shall any Certificateholder be under any liability to any
        third
        person by reason of any action taken by the parties to this Agreement pursuant
        to any provision hereof.

       


      
        
          
          

        

        
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      No
        Certificateholder shall have any right, by virtue of any provision of this
        Agreement, to institute any suit, action or proceeding in equity or at law
        upon
        or under or with respect to this Agreement unless an Event of Default shall
        have
        occurred and be continuing in respect of this Agreement. It is understood
        and
        intended, and is expressly covenanted by each Certificateholder with every
        other
        Certificateholder and the Trustee, that no one or more Holders of Certificates
        shall have any right in any manner whatever by virtue of any provision of
        this
        Agreement to affect, disturb or prejudice the rights of the Holders of any
        other
        such Certificates, or to obtain or seek to obtain priority over or preference
        to
        any other such Holder, or to enforce any right under this Agreement, except
        in
        the manner herein provided and for the equal, ratable and common benefit
        of all
        Certificateholders. For the protection and enforcement of the provisions
        of the
        Section, each and every Certificateholder and the Trustee shall be entitled
        to
        such relief as can be given either at law or in equity.

       

      Section
        8.02. Governing
        Law.
        THIS
        AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
        OF THE
        STATE OF NEW YORK, WITHOUT REFERENCE TO ITS CONFLICT OF LAW PROVISIONS (OTHER
        THAN SECTION 5-1401 OF THE GENERAL OBLIGATIONS LAW), AND THE OBLIGATIONS,
        RIGHTS
        AND REMEDIES OF THE PARTIES HEREUNDER SHALL BE DETERMINED IN ACCORDANCE WITH
        SUCH LAWS.

       

      Section
        8.03. Demands,
        Notices and Communications.
        All
        formal demands, notices and communications by and among the Trustee, the
        Securities Administrator, the Certificate Registrar, the Paying Agent and
        the
        Holder of any Certificate shall be in writing and delivered in person or
        by
        first class mail, postage prepaid, or by facsimile to the Trustee or Securities
        Administrator, as applicable, at its address or facsimile number set forth
        in
        the Underlying Trust Agreement. Any notice so mailed within the time prescribed
        in this Agreement shall be conclusively presumed to have been duly given
        whether
        or not the Person to whom such notice shall have been directed receives such
        notice.

       

      Section
        8.04. Severability
        of Provisions.
        If any
        one or more of the covenants, agreements, provisions or terms of this Agreement
        shall be for any reason whatsoever held invalid, then such covenants,
        agreements, provisions or terms shall be deemed severable from the remaining
        covenants, agreements, provisions or terms of this Agreement and shall in
        no way
        affect the validity or enforceability of the other provisions of this Agreement
        or of the Certificates or the rights of the Holders thereof.

       

      Section
        8.05. Tax
        Status and Reporting.
        (a) It
        is the intended that the Trust Fund created hereunder be considered a “grantor
        trust” under the Code and a WHFIT that is a WHMT. The Securities Administrator
        will report as required under the WHFIT Regulations to
        the
        extent such information as is reasonably necessary to enable the Securities
        Administrator to do so is
        provided to the Securities Administrator on a timely basis. The Securities
        Administrator can assume that the DTC is the only middleman listed as the
        registered holder for the related Certificates. The Securities Administrator
        shall not be liable for any tax reporting penalties that may arise under
        the
        WHFIT Regulations as
        a
        result of the Depositor incorrectly determining the status of the Trust Fund
        as
        a WHFIT.

       


      
        
          
          

        

        
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      (b)
        The
        Securities Administrator shall report required WHFIT information using the
        accrual method. The Securities Administrator shall make available WHFIT
        information to holders annually. In addition, the Securities Administrator
        will
        not be responsible or liable for providing subsequently amended, revised
        or
        updated information to any holder, unless requested by the holder.

       

      (c)
        The
        Securities Administrator shall not be liable for failure to meet the reporting
        requirements of the WHFIT Regulations nor for any penalties thereunder if
        such
        failure is due to: (i) the lack of reasonably necessary information being
        provided to the Securities Administrator, (ii) incomplete, inaccurate or
        untimely information being provided to the Securities Administrator or (iii)
        the
        inability of the Securities Administrator, after good faith efforts, to alter
        its existing information reporting systems to capture information necessary
        to
        fully comply with the WHFIT Regulations for the 2007 calendar year. Each
        owner
        of a Certificate representing, in whole or in part, beneficial ownership
        of an
        interest in a WHFIT, by acceptance of its interest in such Certificate, will
        be
        deemed to have agreed to provide the Securities Administrator with information
        regarding any sale of such Certificate, including the price, amount of proceeds
        and date of sale. Absent receipt of such information, and unless informed
        otherwise by the Depositor, the Securities Administrator may assume there
        is no
        secondary market trading of WHFIT interests.

       

      (d)
        To
        the extent required by the WHFIT Regulations, the Securities Administrator
        shall
        use reasonable efforts to publish on an appropriate website the CUSIPs for
        the
        Certificates that represent ownership of a WHFIT. The CUSIPs so published
        will
        represent the Rule 144A CUSIPs. The Securities Administrator shall make
        reasonable good faith efforts to keep the website accurate and updated to
        the
        extent CUSIPs have been received. Absent the receipt of a CUSIP, the Securities
        Administrator shall use a reasonable identifier number in lieu of a CUSIP.
        The
        Securities Administrator shall not be liable for investor reporting delays
        that
        result from the receipt of inaccurate or untimely CUSIP
        information.

       

      (e)
        For
        federal income tax purposes, the grantor trust created hereunder shall have
        a
        calendar year taxable year. The Securities Administrator shall prepare or
        cause
        to be prepared and shall file or cause to be filed with the Internal Revenue
        Service and applicable state or local tax authorities, income tax information
        returns for each taxable year with respect to the grantor trust.

       


      
        
          
          

        

        
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      IN
        WITNESS WHEREOF, the parties hereto hereby execute this Agreement, as of
        the day
        and year first above written.

       

      


       

      U.S.
        BANK
        NATIONAL ASSOCIATION

      solely
        in
        its capacity as Trustee

       

       

      By:___/s/
        David Duclos_____________

      Name:__David
        Duclos______________

      Title:__Vice
        President______________

       

      


       

      WELLS
        FARGO BANK, N.A.

      as
        Securities Administrator

       

       

      By:____/s/
        Martin Reed_____________

      Name:___Martin
        Reed______________

      Title:___Vice
        President______________

       

      


       

      STRUCTURED
        ASSET SECURITIES 

      CORPORATION

      in
        its
        capacity as Depositor

       

       

      By:____/s/
        Nicholas Stimola__________

      Name:_Nicholas
        Stimola_____________

      Title:_
        Vice
        President_______________

       

      



      
        
          
          

        

        
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      APPENDIX
        A

       

      Available
        Exchange Combinations

      


      
         

        
          	

                  Exchange
                    Certificates

                	 	

                  Exchangeable
                    Certificates

                


        

        
          
            
              	
                      Combination

                    	
                      Maximum
                        Initial Principal Balance/ 

                      Notional
                        Amount
                        (1)

                    	
                      Class

                    	
                      Maximum
                        Initial Principal Balance/ 

                      Notional
                        Amount
                        (1)

                    	
                      Principal
                        Type

                    	
                      Interest
                        Type

                    
	
                    


            

          

        

        
          	 	 	 	 	 	 
	
                  Combination
                    1

                	
                   

                	 	 	 	 
	
                  1-A1

                	
                  $62,310,000

                	
                  1-A3

                	
                  $65,360,000

                	
                  Senior,
                    Pass-Through

                	
                  Fixed
                    Rate

                
	
                  1-A2

                	
                  $
                    3,050,000

                	
                   

                	
                   

                	 	 
	 	
                   

                	
                   

                	
                   

                	 	 
	
                  Combination
                    2

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  2-A9

                	
                  $116,272,000

                	
                  2-A1

                	
                  $125,216,000

                	
                  Senior,
                    Pass-Through

                	
                  Fixed
                    Rate

                
	
                  2-A11

                	
                  $
                    8,944,000

                	
                   

                	
                   

                	 	
                   

                
	
                  2-A12

                	
                  $
                    80,496,000

                	
                   

                	
                   

                	 	 
	 	
                   

                	
                   

                	
                   

                	 	 
	
                  Combination
                    3

                	 	 	 	 	
                   

                
	
                  2-A3

                	
                  $
                    4,713,000

                	
                  2-A5 

                	
                   $129,929,000

                	
                  Senior,
                    Pass-Through

                	
                  Fixed
                    Rate

                
	
                  2-A9

                	
                  $116,272,000

                	
                   

                	
                   

                	 	
                   

                
	
                  2-A11

                	
                  $
                    8,944,000

                	 	 	 	 
	
                  2-A12

                	
                  $
                    80,496,000

                	 	 	 	 
	 	
                   

                	
                   

                	
                   

                	 	 
	
                  Combination
                    4

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  2-A2

                	
                  $44,000,000

                	
                  2-A6

                	
                  $47,442,000

                	
                  Senior,
                    Pass-Through

                	
                  Fixed
                    Rate

                
	
                  2-A4

                	
                  $
                    3,442,000

                	
                   

                	
                   

                	 	
                   

                
	 	 	
                   

                	
                   

                	 	 
	
                  Combination
                    5

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  2-A3

                	
                  $4,713,000

                	
                  2-A7

                	
                  $8,155,000

                	
                  Senior
                    Support, Pass-Through

                	
                  Fixed
                    Rate

                
	
                  2-A4

                	
                  $3,442,000

                	
                   

                	
                   

                	 	
                   

                
	 	 	
                   

                	
                   

                	 	 
	
                  Combination
                    6

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  1-A2

                	
                  $3,050,000

                	
                  2-A8

                	
                  $11,205,000

                	
                  Senior
                    Support, Pass-Through

                	
                  Weighted
                    Average Rate(2)

                
	
                  2-A3

                	
                  $4,713,000

                	 	 	 	 
	
                  2-A4

                	
                  $3,442,000

                	
                   

                	
                   

                	 	
                   

                
	 	 	
                   

                	
                   

                	 	 
	
                  Combination
                    7

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  2-A11

                	
                  $
                    8,944,000

                	
                  2-A10

                	
                  $8,944,000

                	
                  Super
                    Senior, Pass-Through

                	
                  Inverse
                    Floating Rate

                
	
                  2-A12

                	
                  $80,496,000

                	
                   

                	
                   

                	 	
                   

                
	 	 	
                   

                	
                   

                	 	 
	
                  Combination
                    8

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  3-A10

                	
                  $176,102,571

                	
                  3-A1

                	
                  $205,453,000

                	
                  Super
                    Senior, Pass-Through

                	
                  Fixed
                    Rate

                
	
                  3-A12

                	
                  $
                    29,350,429

                	 	 	 	 
	
                  3-A13

                	
                  $
                    58,700,857

                	
                   

                	
                   

                	 	
                   

                
	 	 	 	 	 	 
	
                  Combination
                    9

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  3-A4

                	
                  $30,000,000

                	
                  3-A2

                	
                  $51,362,000

                	
                  Senior
                    Mezzanine, Pass-Through

                	
                  Fixed
                    Rate

                
	
                  3-A5

                	
                  $14,240,000

                	 	 	 	 


        

         

        
          
            
            

          

          
            A-1

            
              

            

          

          
            
            

          

        

         

        
           

          
            	

                    Exchange
                      Certificates

                  	 	

                    Exchangeable
                      Certificates

                  


          

          
            	
                    Combination

                  	
                    Maximum
                      Initial Principal Balance/ 

                    Notional
                      Amount
                      (1)

                  	
                    Class

                  	
                    Maximum
                      Initial Principal Balance/ 

                    Notional
                      Amount
                      (1)

                  	
                    Principal
                      Type

                  	
                    Interest
                      Type

                  
	
                  


          

        

        
          	 	 	 	 	 	 
	
                  3-A6

                	
                  $
                    7,122,000

                	
                   

                	
                   

                	 	
                   

                
	 	 	
                   

                	
                   

                	 	 
	 	 	 	 	 	 
	
                  Combination
                    10

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  3-A5

                	
                  $14,240,000

                	
                  3-A7

                	
                  $21,362,000

                	
                  Senior
                    Mezzanine, Pass-Through

                	
                  Fixed
                    Rate

                
	
                  3-A6

                	
                  $
                    7,122,000

                	 	 	 	 
	 	 	
                   

                	
                   

                	 	
                   

                
	
                  Combination
                    11

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  3-A3

                	
                  $
                    37,668,000

                	
                  3-A9

                	
                  $294,483,000

                	
                  Senior,
                    Pass-Through

                	
                  Fixed
                    Rate

                
	
                  3-A4

                	
                  $
                    30,000,000

                	 	 	 	 
	
                  3-A5

                	
                  $
                    14,240,000

                	
                   

                	
                   

                	 	
                   

                
	
                  3-A6

                	
                  $
                    7,122,000

                	 	 	 	 
	
                  3-A10

                	
                  $176,102,571

                	
                   

                	
                   

                	 	 
	
                  3-A12

                	
                  $
                    29,350,429

                	 	 	 	 
	
                  3-A13

                	
                  $
                    58,700,857

                	
                   

                	
                   

                	 	 
	 	 	 	 	 	 
	
                  Combination
                    12

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  3-A12

                	
                  $
                    29,350,429

                	
                  3-A11

                	
                  $29,350,429

                	
                  Super
                    Senior, Pass-Through

                	
                  Inverse
                    Floating Rate

                
	
                  3-A13

                	
                  $
                    58,700,857

                	 	 	 	 
	 	 	 	 	 	 
	
                  Combination
                    13

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  4-A2

                	
                  $16,288,000

                	
                  4-A1

                	
                  $32,576,000

                	
                  Super
                    Senior, Pass-Through

                	
                  Fixed
                    Rate

                
	
                  4-A3

                	
                  $16,288,000

                	 	 	 	 
	 	 	 	 	 	 
	
                  Combination
                    14

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  4-A2

                	
                  $16,288,000

                	
                  4-A5

                	
                  $38,410,000

                	
                  Senior,
                    Pass-Through

                	
                  Fixed
                    Rate

                
	
                  4-A3

                	
                  $16,288,000

                	 	 	 	 
	
                  4-A4

                	
                  $
                    5,834,000

                	 	 	 	 
	 	 	 	 	 	 
	
                  Combination
                    15

                	
                   

                	
                   

                	
                   

                	 	
                   

                
	
                  AP2

                	
                  $
                    950,330

                	
                  AP4

                	
                  $3,528,003

                	
                  Senior,
                    Ratio-Strip, Principal-Only

                	
                  Not
                    Applicable

                
	
                  AP3

                	
                  $2,577,673

                	 	 	 	 


        


         

      

      
        	
                (1)

              	
                Exchange
                  Certificates and Exchangeable Certificates in any combination may
                  be
                  exchanged only in the proportion that the maximum initial principal
                  balances or notional amounts of such certificates bear to one another
                  as
                  shown above.

              


      

      
        	
                (2)

              	
                The
                  weighted average rate applicable to this formula will be based
                  on the
                  weighted average of the certificate interest rates of the related
                  Exchange
                  Certificates.

              


      


      
        
          
          

        

        
          A-2

          
            

          

        

        
          
          

        

      


      


      EXHIBIT
        I

      


      FORM
        OF EXCHANGE LETTER

      


      


      


      


      ___,
        20__

      


      


      Wells
        Fargo Bank, N.A.

      Sixth
        Street and Marquette Avenue

      Minneapolis,
        Minnesota 55479

      Attention:
        Corporate Trust Services, LMT 2007-10

      


      


      
        	
                Re:

              	Lehman Mortgage
                Trust 2007-10,
	 	Mortgage Pass-Through Certificates,
                Series 2007-10


      

       

      Ladies
        and Gentlemen:

      


      Pursuant
        to the terms of the Exchange Trust Agreement dated as of November 1, 2007
        (the
“Trust
        Agreement”),
        by
        and among Structured Asset Securities Corporation, as depositor, Wells Fargo
        Bank, N.A., as securities administrator (the “Securities
        Administrator”)
        and
        U.S. Bank National Association, as trustee (the “Trustee”),
        we
        hereby present and surrender the Certificates specified on Schedule
        I
        attached
        hereto and transfer, assign, set over and otherwise convey to the Trustee,
        all
        of our right, title and interest in and to such Certificates, including all
        payments of interest thereon received after [___________], 2007, in exchange
        for
        the related Certificates specified on Schedule
        I
        attached
        hereto. 

       

      We
        agree
        that upon such exchange the portions of the Certificates designated for exchange
        shall be deemed cancelled and replaced by the Certificates issued in exchange
        therefor. We confirm that we have paid a fee to the Securities Administrator
        in
        connection with such exchange equal to $5,000.

       



      
        
          
          

        

        
          I-1

          
            

          

        

        
          
          

        

      


      Sincerely,

      


      


      


      By:
              

      Name:
        

      Title:
        

      


      Acknowledged
        by:

      


      WELLS
        FARGO BANK, N.A., 

      as
        Securities Administrator

      


      


      By:
              

      Name:
        

      Title:

      



      
        
          
          

        

        
          I-2

          
            

          

        

        
          
          

        

      


      SCHEDULE
        I

      


      [insert
        the information as to the Exchange Class(es) and Exchangeable Class(es) to
        be
        exchanged required by Section 2.04 of the Agreement]


      
        
          
          

        

        
          I-3