Exhibit 10.51


                     THIRD AMENDMENT TO AMENDED AND RESTATED
                       AGREEMENT OF LIMITED PARTNERSHIP OF
                        PSA INSTITUTIONAL PARTNERS, L.P.,
                        A CALIFORNIA LIMITED PARTNERSHIP

                       (CREATING SERIES Z PREFERRED UNITS)


         This Third Amendment (the "AMENDMENT") to the Amended and Restated
Agreement of Limited Partnership of PSA Institutional Partners, L.P., a
California Limited Partnership dated March 29, 2000 as amended by the Amendment
to Amended and Restated Agreement of Limited Partnership of PSA Institutional
Partners, L.P., dated as of August 11, 2000. and the Second Amendment to Amended
and Restated Agreement of Limited Partnership of PSA Institutional Partners,
L.P., dated as of March 22, 2004 (the "Partnership Agreement") is made and
entered into as of October 12, 2004 (the "Effective Date") with reference to the
following facts:

         A. Pursuant to Section 3.3 of the  Partnership  Agreement,  the General
Partner is authorized to cause the Partnership to issue certain additional units
of limited partnership interest without the consent of the Limited Partners.

         B.The General  Partner has determined  that it is in the best interests
of the  Partnership  to  create a new  class of  units,  with the  designations,
preferences and other rights, powers and duties set forth in this Amendment,  to
be known as Series Z  Preferred  Units,  and to issue  those  units as set forth
below.

         C. Unlessotherwise  defined in this Amendment,  capitalized terms shall
have the meanings given to them in the Partnership Agreement.

         The parties agree as follows:

         1. The  following  definition  shall be inserted  into Section 1 of the
Partnership Agreement in the appropriate alphabetical order:

         "SERIES Z PREFERRED UNITS" means the series of partnership interests
         designated as the "6.250% Series Z Cumulative Redeemable Perpetual
         Preferred Units" entitled to the rights described in this Agreement.
         The Series Z Preferred Units are Exchangeable Preferred Units, and the
         Corresponding Preferred Stock with respect to those units is the 6.250%
         Cumulative Preferred Stock, Series Z, of the Company."

         2. The definition of "PRIORITY RETURN" in the Partnership  Agreement is
amended by inserting the following at the end of clause (i):

         "and for the Series Z Preferred Units an amount equal to six and
         twenty-five hundredths percent (6.250%) per annum of the stated value
         of $25 per unit,"

In addition, notwithstanding anything to the contrary in the Partnership
Agreement, to reflect the issuance of certain Series Z Preferred Units as of the
Effective Date, the Priority Return relating to the quarter in 2004 in which
those Series Z Preferred Units are issued shall be 78/90ths of the Priority
Return that would accrue for a full calendar quarter.

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         3. The  definition  of  "PARITY  PREFERRED  UNITS"  in the  Partnership
Agreement  shall be amended by inserting the phrase "Series Z Preferred  Units,"
into the second sentence after the phrase "Series NN Preferred Units".

         4. On the Effective  Date,in  accordance with that certain Purchase and
Contribution  Agreement  dated as of June 9,  2004  among  Secure  Mini  Storage
Limited   Partnership   (the   "Acquired   Partnership"),   its  partners   (the
"Contributors"),  he  Partnership  and the General  Partner  (the  "Contribution
Agreement"),   the  Contributors  shall  make  a  capital  contribution  to  the
Partnership of a 99.5% limited partnership  interest in the Acquired Partnership
and concurrently one of the Contributors., shall sell a 0.5% general partnership
interest in the  Acquired  Partnership  to the  General  Partner  (together  the
transferred  interests  representing all interests in the Acquired  Partnership)
and the Partnership  shall issue to two of the  Contributors  1,000,000 Series Z
Preferred Units and  concurrently  distribute to the Contributors the portion of
the Cash  Consideration  that is payable by the  Partnership  as provided in the
Contribution  Agreement  and the General  Partner  shall pay to the  Contributor
selling the general partner interest the portion of the Cash  Consideration that
is payable by the General Partner as provided in the Contribution  Agreement. In
order to  reflect  the  issuance  of  those  Series Z  Preferred  Units,  on the
Effective  Date,  Exhibit A to the  Partnership  Agreement  is replaced  with an
updated Exhibit A reflecting the Series Z Preferred Units.

         5.  Section  3.2 of the  Partnership  Agreement  is  amended to add the
addresses of the Contributors.

         6. Section 6.6.1 of the Partnership Agreement is amended to read in its
entirety as follows:

                   "6.6.1. RIGHT OF OPTIONAL REDEMPTION. The Series N, Series O
         and Series P Preferred Units may not be redeemed prior to the fifth
         (5th) anniversary of the issuance date of the particular series to be
         redeemed. The Series NN Preferred Units may not be redeemed prior to
         March 17, 2010. The Series Z Preferred Units may not be redeemed prior
         to March 5, 2009. On or after the fifth anniversary of the issuance
         date of each of the Series N, Series O and Series P Preferred Units,
         and on or after March 17, 2010 with respect to the Series NN Preferred
         Units, and on or after March 5, 2009 with respect to the Series Z
         Preferred Units, the Partnership shall have the right to redeem the
         Series N, Series O, Series P, Series NN Preferred Units or Series Z
         Preferred Units, respectively, in whole or in part, at any time or from
         time to time, upon not less than thirty (30) nor more than sixty (60)
         days' written notice, at a redemption price, payable in cash, equal to
         the Liquidation Preference per Series N, Series O, Series P, Series NN
         or Series Z Preferred Unit to be redeemed (the "Redemption Price"). The
         rights of redemption of any subsequently issued Parity Preferred Units
         shall be as designated in an amended Exhibit A to this Agreement. If
         fewer than all of the outstanding Parity Preferred Units of a
         particular series are to be redeemed, the units to be redeemed from
         that series shall be selected pro rata (as nearly as practicable
         without creating fractional units)."

         7. Section 6.7 of the  Partnership  Agreement is amended to read in its
entirety as follows:

                  "6.7 NO SINKING FUND. No sinking fund shall be established for
         the retirement or redemption of Series N, Series NN, Series O, Series P
         or Series Z Preferred Units."

         8.  Section  10.3 of the  Partnership  Agreement is amended to renumber
Section  10.3.3  (added and  inadvertently  misnumbered  pursuant  to the Second
Amendment)  as Section  10.3.1  and to add  immediately  after  that  renumbered
provision the following Section 10.3.2:

                  "10.3.2 SERIES Z PREFERRED UNITS. Holders of the Series Z
         Preferred Units will not have any voting rights or right to consent to
         any matter requiring the consent or approval of the Limited Partners,
         except as set forth below. So long as any Series Z Preferred Units
         remain outstanding, the Partnership shall not, without the affirmative
         vote of the holders of at least a majority of the Series Z Preferred
         Units outstanding at the time, take any of the actions described above
         in Sections 10.2.1, 10.2.2 and 10.2.3, treating each reference in those
         provisions to "Series N Preferred Units" as a reference instead to
         "Series Z Preferred Units."

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         9.  Section  12.2 of the  Partnership  Agreement  is  amended by adding
immediately after Section 12.2.3 the following Section 12.2.4:

                   "12.2.4 SERIES Z PREFERRED UNITS. At any time on or after the
         first (1st) anniversary of the date of issuance of Series Z Preferred
         Units, each holder of Series Z Preferred Units shall have the option to
         exchange such holder's Series Z Preferred Units for depositary shares
         representing interests in authorized but previously unissued shares of
         6.250% Cumulative Preferred Stock, Series Z, of the Company (the
         "Series Z Preferred Stock") at an exchange rate of one depositary share
         representing one thousandth (1/1000) of a share of Series Z Preferred
         Stock for one (1) Series Z Preferred Unit, subject to adjustment as
         described below (the "Exchange Ratio"), provided that each such
         exchange must involve a minimum of: (i) 200,000 Series Z Preferred
         Units or (ii) if less than 200,000 Series Z Preferred Units are then
         outstanding, all outstanding Series Z Preferred Units. At any time on
         or after March 5, 2009, the Company also shall have the option to cause
         each holder to so exchange all, but not part, of the holder's Series Z
         Preferred Units.

                  In the event the Registration Statement on Form S-3
         contemplated by Section 7.13 of the SMS Contribution Agreement relating
         to the Series Z Preferred Units has not been declared effective by the
         first (1st) anniversary of the date of issuance of Series Z Preferred
         Units, the Company may delay any exchange requested pursuant to Section
         12.3 (during which period the holder exercising the exchange right may
         withdraw the related Exchange Notice (as defined in Section 12.3.1))
         until such time as such Registration Statement is declared effective,
         provided that the Company continues to use it reasonable best efforts
         to cause such Registration Statement to become effective as promptly as
         possible.

                  The provisions of Sections 12.1.5 and 12.1.6 shall be read as
         if restated in this Section 12.2.4, but: as if each reference in those
         provisions to "Series N Preferred Units" instead were a reference to
         "Series Z Preferred Units," and by treating each reference to the
         "Series N Preferred Stock" as a reference to the 6.250% Cumulative
         Preferred Stock, Series Z, of the Company."

         10. The provisions of Section 12.3.1 of the Partnership Agreement shall
be read,  in the case of the Series Z  Preferred  Units,  as if the term  "fifth
(5th) Business Day" were replaced with the term "tenth (10th) Business Day."

         11.Upon not less than 120 nor more than 180 days' written notice to the
Partnership  in advance of the fifth  anniversary  of the  Effective  Date,  the
holders of a majority of the then  outstanding  Series Z  Preferred  Units shall
have the one time election to cause the Company (or at the Company's  option, an
affiliate,  which  may  include  the  Partnership)  to  repurchase  on the fifth
anniversary of the Effective Date all then outstanding  Series Z Preferred Units
at a price  payable in cash  equal to the  Liquidation  Preference  per Series Z
Preferred Unit.

         12. Prior to the fifth anniversary of the Effective Date, the
Partnership agrees that it will not, without the prior written consent of an
affected partner (either of two of the Contributors), which consent will not be
unreasonably withheld, voluntarily permit the disposition in a transaction that
will cause material recognition of taxable gain for federal income tax purposes
to the affected partner of any of the 26 real properties held by the Acquired
Partnership on the Effective Date (as well as any subsequently acquired
property, the federal income tax basis of which is determined by reference to
the federal income tax basis of those existing properties, such as a replacement
property that might be acquired in a "like-kind exchange" for an existing
property). The limitations on dispositions in the preceding sentence shall not
apply if, at the time of the proposed disposition, the affected partner then
owns less than 30% of the Series Z Preferred Units acquired by the affected
partner as of the date of this Amendment.

         13. Except as expressly provided in this Amendment, all of the
provisions of the Partnership Agreement are ratified and confirmed, and continue
in full force and effect.

The undersigned have signed this Amendment as of the date indicated above.

                         [signatures on following pages]

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                          "GENERAL PARTNER:"


                          PS TEXAS HOLDINGS, LTD.,
                          a Texas limited partnership

                          By: PS GPT Properties, Inc., a California corporation,
                              its general partner


                          By: /s/ John S. Baumann
                              -------------------
                              Name:  John S. Baumann
                              Title: Senior Vice President


                          "LIMITED PARTNERS:"

                          PS LPT PROPERTIES INVESTORS, INC.
                          a Maryland business trust


                          By: /s/ John S. Baumann
                              -------------------
                              Name:  John S. Baumann
                              Title: Senior Vice President


                              [signatures continue]

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The undersigned have signed this Agreement of Limited Partnership as of the date
indicated above.



                          By:  the Contributors




                              [signatures continue]

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                           ALL OTHER LIMITED PARTNERS

                           By:PS Texas Holdings, Ltd.,
                              a Texas limited partnership,
                              as their attorney-in-fact


                              By: PS GPT Properties, Inc.,
                                  a California corporation,
                                  its general partner


                                  By: /s/ John S. Baumann
                                      -------------------
                                      Name:  John S. Baumann
                                      Title: Senior Vice President


                              [signatures continue]

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              ACKNOWLEDGED AND AGREED, AS TO THE
              ISSUANCE OF COMPANY STOCK PURSUANT
              TO SECTION 12 OF THE PARTNERSHIP AGREEMENT:


"COMPANY"

PUBLIC STORAGE, INC.,
a California corporation


By: /s/ John S. Baumann
    -------------------
    Name:  John S. Baumann
    Title: Senior Vice President

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