Document:

<PAGE>
                                                                    EXHIBIT 10.4

                             SUPPLEMENTAL INDENTURE

         Supplemental Indenture (this "Supplemental Indenture"), dated as of
February 21, 2002, by and among Dura G.P., a Delaware general partnership (the
"Guaranteeing Subsidiary"), Dura Operating Corp., a Delaware corporation (the
"Issuer"), Dura Automotive Systems, Inc., a Delaware corporation ("Parent"),
Dura Automotive Systems Cable Operations, Inc., a Delaware corporation,
Universal Tool & Stamping Company Inc., an Indiana corporation, Adwest
Electronics, Inc., a Delaware corporation, Dura Automotive Systems of Indiana,
Inc., an Indiana corporation, Atwood Automotive Inc., a Michigan corporation and
Mark I Molded Plastics of Tennessee, Inc., a Tennessee corporation, Atwood
Mobile Products, Inc., an Illinois corporation (together with Parent, the
"Existing Guarantors"), and U.S. Bank Trust National Association, as trustee
(the "Trustee") under the Indentures (as hereinafter defined). Capitalized terms
used herein without definition shall have the meanings assigned to them in the
Indentures.

         W I T N E S S E T H

         WHEREAS, the Issuer and the Existing Guarantors have previously
executed and delivered to the Trustee (i) an indenture, dated as of April 22,
1999, providing for the issuance of an aggregate principal amount of up to
$350,000,000 of 9% Senior Subordinated Notes due 2009, (ii) an indenture, dated
as of April 22, 1999, providing for the issuance of an aggregate principal
amount of up to 150,000,000 of 9% Senior Subordinated Notes due 2009; and (iii)
an indenture, dated as of June 22, 2001, providing for the issuance of an
aggregate principal amount of up to$600,000,000 of 9% Senior Subordinated Notes
due 2009 (collectively, and as supplemented and amended from time to time, the
"Indentures");

         WHEREAS, pursuant to Section 4.17 of the Indentures, the Guaranteeing
Subsidiary is required to become a Guarantor and execute a supplemental
indenture to the Indentures; and

         WHEREAS, pursuant to Section 9.06 of the Indentures, the Trustee is
authorized to execute and deliver this Supplemental Indenture;

         NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the parties
hereto mutually covenant and agree for the equal and ratable benefit of the
Holders of the Notes as follows:

         1. Agreement to Guarantee. The Guaranteeing Subsidiary hereby agrees as
follows:

            (1)   Along with all Guarantors named in the Indentures, to
                  unconditionally guarantee (each such guarantee to be referred
                  to herein as a "Note Guarantee") to each Holder of a Note
                  authenticated and delivered by the Trustee and to the Trustee
                  and its successors and assigns, irrespective of the validity
                  and enforceability of this Supplemental Indenture, the Notes
                  or the obligations of the Issuer hereunder or thereunder,
                  that: (i) the principal of and interest on the Notes will be
                  promptly paid in full when due, whether at

<PAGE>

                  maturity, by acceleration, redemption or otherwise, and
                  interest on the overdue principal of and interest on the
                  Notes, if any, if lawful, and all other obligations of the
                  Issuer to the Holders or the Trustee hereunder or thereunder
                  will be promptly paid in full or performed, all in accordance
                  with the terms hereof and thereof; and (ii) in case of any
                  extension of time of payment or renewal of any Notes or any of
                  such other obligations, that same will be promptly paid in
                  full when due or performed in accordance with the terms of the
                  extension or renewal, whether at stated maturity, by
                  acceleration or otherwise. Failing payment when due of any
                  amount so guaranteed or any performance so guaranteed for
                  whatever reason, the Guaranteeing Subsidiary shall be jointly
                  and severally obligated to pay the same immediately. The
                  Guaranteeing Subsidiary agrees that this is a guarantee of
                  payment and not a guarantee of collection.

         (2)      The Guaranteeing Subsidiary hereby agrees that its obligations
                  hereunder shall be unconditional, irrespective of the
                  validity, regularity or enforceability of the Notes or this
                  Supplemental Indenture, the absence of any action to enforce
                  the same, any waiver or consent by any Holder of the Notes
                  with respect to any provisions hereof or thereof, the recovery
                  of any judgment against the Issuer, any action to enforce the
                  same or any other circumstance which might otherwise
                  constitute a legal or equitable discharge or defense of any
                  other Guarantor. The Guaranteeing Subsidiary hereby waives
                  diligence, presentment, demand of payment, filing of claims
                  with a court in the event of insolvency or bankruptcy of the
                  Issuer, any right to require a proceeding first against the
                  Issuer, protest, notice and all demands whatsoever and
                  covenants that its Note Guarantee shall not be discharged
                  except by complete performance of the obligations contained in
                  the Notes, the Indentures and this Note Guarantee.

         (3)      If any Holder or the Trustee is required by any court or
                  otherwise to return to the Issuer, to any Guarantor, or any
                  custodian, trustee, liquidator or other similar official
                  acting in relation to either the Issuer or to any Guarantor,
                  any amount paid by either to the Trustee or such Holder, the
                  Note Guarantee, to the extent theretofore discharged, shall be
                  reinstated in full force and effect.

         (4)      The Guaranteeing Subsidiary agrees that it shall not be
                  entitled to any right of subrogation in relation to the
                  Holders in respect of any Note Guarantee until payment in full
                  of all obligations guaranteed under this Supplemental
                  Indenture. The Guaranteeing Subsidiary further agrees that, as
                  between it, on the one hand, and the Holders and the Trustee,
                  on the other hand, (x) the maturity of the obligations
                  guaranteed hereby may be accelerated as provided in Article 6
                  of the Indentures for the purposes of this Note Guarantee,
                  notwithstanding any stay, injunction or other prohibition
                  preventing such

                                       2
<PAGE>

                  acceleration in respect of the obligations guaranteed hereby,
                  and (y) in the event of any declaration of acceleration of
                  such obligations as provided in Article 6 of the Indentures,
                  such obligations (whether or not due and payable) shall
                  forthwith become due and payable by the Guaranteeing
                  Subsidiary for the purpose of this Note Guarantee. The
                  Guaranteeing Subsidiary shall have the right to seek
                  contribution from any non-paying Guarantor so long as the
                  exercise of such right does not impair the rights of the
                  Holders under this Note Guarantee.

         2. Incorporation of Terms of Indentures. The obligations of the
Guaranteeing Subsidiary under the Note Guarantees shall be governed in all
respects by the terms of the Indentures and shall constitute a Guarantee
thereunder. Each of the parties hereto shall be bound by the terms of the
Indentures as they relate to the Note Guarantees.

         3. No Recourse Against Others. No stockholder, officer, director,
employee or incorporator, past, present or future, or the Guaranteeing
Subsidiary, as such, shall have any personal liability under this Note Guarantee
by reason of his, her or its status as such stockholder, officer, director,
employee or incorporator.

         4. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK
SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT
GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT
THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

         5. Counterparts. The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.

         6. Effect of Headings. The Section headings herein are for convenience
only and shall not affect the construction hereof.

         7. Disclaimer by Trustee. The Trustee makes no representation as to the
validity of this Supplemental Indenture or the proper authorization or due
execution of this Supplemental Indenture by the Issuer, the Existing Guarantors
or the Guaranteeing Subsidiary.

                                    * * * * *

                                       3
<PAGE>

                  IN WITNESS WHEREOF, the parties hereto have caused this
Supplemental Indenture to be duly executed and attested, all as of the date
first above written.

         Dated: February 21, 2002

                                                 DURA G.P.

                                                 By:      Dura Operating Corp.

                                                 Its:     General Partner

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Assistant Secretary

                                                 DURA OPERATING CORP.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Assistant Secretary

                                                 DURA AUTOMOTIVE SYSTEMS CABLE
                                                 OPERATIONS, INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

<PAGE>

                [Signature Page to Supplemental Indenture cont.]

                                                 UNIVERSAL TOOL & STAMPING
                                                 COMPANY INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

                                                 ADWEST ELECTRONICS, INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

                                                 DURA AUTOMOTIVE SYSTEMS OF
                                                 INDIANA, INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

                                                 ATWOOD AUTOMOTIVE INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

<PAGE>

                [Signature Page to Supplemental Indenture cont.]

                                                 MARK I MOLDED PLASTICS OF
                                                 TENNESSEE, INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

                                                 DURA AUTOMOTIVE SYSTEMS, INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Assistant Secretary

                                                 ATWOOD MOBILE PRODUCTS, INC.

                                                 By:    /s/ David R. Bovee
                                                        ------------------------
                                                 Name:  David R. Bovee

                                                 Its:   President, Chief
                                                        Financial Officer and
                                                        Treasurer

<PAGE>

                [Signature Page to Supplemental Indenture cont.]

                                                 U.S. BANK TRUST NATIONAL
                                                 ASSOCIATION, as Trustee

                                                 By:    /s/ Richard Prokosch
                                                        ------------------------

                                                 Name:  Richard Prokosch
                                                        ------------------------

                                                 Its:   Vice President
                                                        ------------------------<PAGE>
                                                                    EXHIBIT 10.5

                        TRANCHE C TERM LOAN SUPPLEMENT TO
                     AMENDED AND RESTATED CREDIT AGREEMENT

         This TRANCHE C TERM LOAN SUPPLEMENT TO AMENDED AND RESTATED CREDIT
AGREEMENT dated as of April 18, 2002 (this "Supplement") is entered into among
DURA OPERATING CORP. ("Dura"), the FINANCIAL INSTITUTIONS LISTED ON THE
SIGNATURE PAGES HEREOF (the "Tranche C Term Lenders"), and BANK OF AMERICA,
N.A., as agent for the Lenders under the Agreement referred to below (the
"Agent").

                                    RECITALS

         A. Dura Automotive Systems, Inc., Dura and certain subsidiaries of
Dura, certain financial institutions and the Agent are parties to that certain
Amended and Restated Credit Agreement dated as of March 19, 1999, as amended as
of May 10, 2001, June 15, 2001, August 24, 2001 and April 17, 2002 (the
"Agreement").

         B. Pursuant to Section 2.17 of the Fourth Amendment dated as of April
17, 2002 to the Agreement, Dura, the Tranche C Term Lenders and the Agent are
entering into this Supplement to provide for the making of Tranche C Term Loans
by the Tranche C Term Lenders to Dura, to specify certain terms of the Tranche C
Term Loans and to join the Tranche C Term Lenders as parties to the Agreement as
Lenders thereunder.

         NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties agree as follows:

         1. Certain Defined Terms. Capitalized terms which are used herein
without definition and that are defined in the Agreement shall have the same
meanings herein as in the Agreement.

         2. Tranche C Term Loans.

                  2.1 Tranche C Term Loans. Each Tranche C Term Lender severally
agrees, on the terms and conditions set forth herein, to make loans in U.S.
Dollars to Dura (each such loan, a "Tranche C Term Loan") on April 18, 2002 in
an aggregate Dollar Equivalent amount not to exceed at any time outstanding the
amount set forth opposite such Tranche C Term Lender's name under the heading
"Tranche C Term Loan" on Schedule 2.1 hereto; provided that

                  (i) after giving effect to the Borrowing of the Tranche C Term
         Loans, the outstanding principal Dollar Equivalent amount of all
         Tranche C Term Loans shall not exceed U.S.$150,000,000; and

<PAGE>

                  (ii) after giving effect to the Borrowing of the Tranche C
         Term Loans, the amount of such Tranche C Term Lender's Tranche C Term
         Loans shall not exceed such Tranche C Term Lender's Pro Rata Share of
         all then outstanding Tranche C Term Loans.

 Amounts borrowed as Tranche C Term Loans which are repaid or prepaid may not be
 reborrowed. The obligation of the Tranche C Term Lenders to make Tranche C Term
 Loans shall expire concurrently on the earlier of (A) April 30, 2002 and (B)
 the date on which Tranche C Term Loans are made hereunder. The proceeds of all
 Tranche C Term Loans shall be used to prepay Tranche B Term Loans.

                  2.2 Number of Interest Periods. After giving effect to the
 Borrowing or any conversion or continuation of the Tranche C Term Loans, there
 may not be in effect more than three different Interest Periods for all Tranche
 C Term Loans.

                  2.3 Repayment. Dura shall repay the Tranche C Term Loans in
 installments as set forth in Schedule 2.3 hereto, with the remaining
 outstanding principal amount of all Tranche C Term Loans being payable in full
 on December 31, 2008.

                  2.4 Interest. Each Tranche C Term Loan shall bear interest on
 the outstanding principal amount thereof from the date on which such Tranche C
 Term Loan is made to the date payment thereof is due at a rate per annum equal
 to the Offshore Rate plus 2.50% or the U.S. Base Rate plus 1.00%, as the case
 may be (and subject to Dura's right to convert to the other Type of Loan under
 Section 2.4 of the Agreement).

                  2.5 Conditions to Making of Tranche C Term Loans. In addition
 to the conditions precedent to borrowing set forth in Section 8.4 of the
 Agreement, the obligation of each Tranche C Term Lender to make its Tranche C
 Term Loan is subject to the following conditions that:

                  (a) the "Amendment Effective Date" under and as defined in the
 Fourth Amendment dated as of April 17, 2002 to the Agreement shall have
 occurred or be occurring concurrently with the making of such Tranche C Term
 Loan;

                  (b) receipt by the Agent of Notes executed by Dura payable to
 the order of the Tranche C Term Lenders evidencing the Tranche C Term Loans;

                  (c) receipt by the Agent of counterparts of this Supplement
 (whether by facsimile or otherwise) executed by Dura, the Agent and the Tranche
 C Term Lenders; and

                  (d) receipt by the Agent of the following, each in form and
substance reasonably satisfactory to the Agent: (i) a certificate of Dura as to
authorizing resolutions with respect to this Supplement and the incumbency and
signatures of officers, and (ii) an opinion of U.S. counsel to DASI and the
Borrowers as to this Supplement.

                                       -2-

<PAGE>
                  2.6 Collateral Matters. Within 60 days of the making of the
Tranche C Term Loans, (x) Dura shall, and shall cause the other Loan Parties to,
enter into such amendments to Mortgages and other Collateral Documents and take
such other actions as the Agent or the Required Lenders may from time to time
reasonably request to assure that the first priority security interest or
mortgage of the Agent in all Collateral continues to secure all Obligations,
including all obligations in respect of the Tranche C Term Loans, and (y) Dura
shall cause the Guarantors to reaffirm their Guaranties.

                  2.7 Lenders. With effect on and after the date the conditions
set forth in Section 2.5 hereof are met, each Tranche C Term Lender shall be a
party to the Agreement as a Lender and have all of the rights and be obligated
to perform all of the obligations of a Lender under the Credit Agreement,
including the requirements concerning confidentiality and the payment of
indemnification. Each Tranche C Term Lender agrees that it will perform in
accordance with their terms all of the obligations which by the terms of the
Agreement are required to be performed by it as a Lender.

                  2.8 Independent Credit Decision. Each Tranche C Term Lender
(a) acknowledges that it has received a copy of the Agreement and the Schedules
and Exhibits thereto, together with copies of the most recent financial
statements referred to in Section 10.1 of the Agreement, and such other
documents and information as it has deemed appropriate to make its own credit
and legal analysis and decision to enter into this Supplement and the Agreement;
and (b) agrees that it will, independently and without reliance upon the
Arranger, the Agents or any other Lender and based on such documents and
information as it shall deem appropriate at the time, continue to make its own
credit and legal decisions in taking or not taking action under the Agreement.

         3. Representations and Warranties. Dura hereby represents and warrants
to the Agent and the Lenders, including the Tranche C Term Lenders, as follows:

                  (i) Representations and Warranties. The representations and
         warranties contained in Article IX of the Agreement are true and
         correct in all material respects as of the date hereof (except to the
         extent such representations and warranties expressly refer to an
         earlier date, in which case they are true and correct as of such
         earlier date).

                  (ii) Enforceability. The execution and delivery by Dura of
         this Supplement, and the performance by Dura of this Supplement and the
         Agreement, as amended hereby, are within the corporate powers of Dura
         and have been duly authorized by all necessary corporate action on the
         part of Dura. This Supplement and the Agreement, as amended hereby, are
         valid and legally binding obligations of Dura, enforceable in
         accordance with their terms, except as enforceability may be limited by
         applicable bankruptcy, insolvency or similar laws affecting the
         enforcement of creditors' rights generally or by equitable principles
         relating to enforceability.

                                       -3-

<PAGE>
                  (iii) No Default. No Event of Default or Unmatured Event of
         Default has occurred and is continuing.

                  (iv) No Material Adverse Effect. No Material Adverse Effect
         has occurred and is continuing since December 31, 2001.

         4. Effect of Supplement. Except as expressly amended and modified by
this Supplement, all provisions of the Agreement shall remain in full force and
effect; and Dura confirms and reaffirms its Obligations under the Agreement as
amended by this Supplement. After this Supplement becomes effective, all
references in the Agreement (or in any other Loan Document) to "this Agreement",
"hereof", "herein" or words of similar effect referring to the Agreement shall
be deemed to be references to the Agreement as amended by this Supplement. This
Supplement shall not be deemed to expressly or impliedly waive, amend or
supplement any provision of the Agreement other than as set forth herein.

         5. Counterparts. This Supplement may be executed in any number of
counterparts and by different parties on separate counterparts, and each
counterpart shall be deemed to be an original, and all such counterparts shall
together constitute but one and the same instrument. A facsimile of the
signature of any party on any counterpart shall be effective as the signature of
the party executing such counterpart for purposes of the effectiveness of this
Supplement.

         6. Governing Law. This Supplement shall be governed by, and construed
in accordance with, the internal laws of the State of Illinois; provided that
the Agent and the Lenders shall retain all rights arising under Federal law.

         7. Section Headings. The various headings of this Supplement are
inserted for convenience only and shall not affect the meaning or interpretation
of this Supplement or the Agreement or any provision hereof or thereof.

                      [signature pages begin on next page]

                                       -4-

<PAGE>
         IN WITNESS WHEREOF, the parties have executed this Supplement as of the
date first above written.

                                              DURA OPERATING CORP.

                                              By: /s/ DAVID R. BOVEE
                                                 ------------------------
                                              Title: VICE PRESIDENT & CFO
                                                    ---------------------

                                       S-1

<PAGE>

                                         BANK OF AMERICA, N.A., as Agent

                                         By: /s/ DAVID PRICE
                                            ------------------
                                         Title: VICE PRESIDENT
                                               ---------------

                                         TRANCHE C TERM LENDERS

                                         BANK OF AMERICA, N.A., as a Tranche C
                                         Term Lender

                                         By: /s/ EDWARD HARMON
                                            ------------------
                                         Title: VICE PRESIDENT
                                               ---------------

                                       S-2

<PAGE>

                                  SCHEDULE 2.1
                        TO TRANCHE C TERM LOAN SUPPLEMENT

TRANCHE C TERM LENDER                       TRANCHE C TERM LOAN

Bank of America, N.A.                       U.S.$150,000,000

<PAGE>

                                  SCHEDULE 2.3
                        TO TRANCHE C TERM LOAN SUPPLEMENT

                 Scheduled Amortization of Tranche C Term Loans

<Table>
<Caption>
Payment Date                   Principal Amount to be Repaid
                               (as a percentage of the original
                               Tranche C Term Loan)
<S>                            <C>
09/30/2002                             0.25%
12/31/2002                             0.25%
03/31/2003                             0.25%
06/30/2003                             0.25%
09/30/2003                             0.25%
12/31/2003                             0.25%
03/31/2004                             0.25%
06/30/2004                             0.25%
09/30/2004                             0.25%
12/31/2004                             0.25%
03/31/2005                             0.25%
06/30/2005                             0.25%
09/30/2005                             0.25%
12/31/2005                             0.25%
03/31/2006                             0.25%
06/30/2006                             0.25%
09/30/2006                             0.25%
12/31/2006                             0.25%
03/31/2007                             0.25%
06/30/2007                             0.25%
09/30/2007                             0.25%
12/31/2007                             0.25%
03/31/2008                           23.625%
06/30/2008                           23.625%
09/30/2008                           23.625%
12/31/2008                           23.625%
                                     -------
                                     100.00%
                                     =======
</Table>

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