Exhibit 10.23

FOURTH AMENDMENT TO CREDIT AGREEMENT
------------------------------------

         THIS FOURTH  AMENDMENT TO CREDIT  AGREEMENT  ("Amendment")  is made and
entered into as of June 27, 2001 (the "Effective  Date"),  by and between NESCO,
Inc., an Oklahoma corporation (the "Borrower"),  and Bank One, Oklahoma, N.A., a
national banking association (the "Lender"), with reference to the following:

         A. The  Borrower  and the Lender are  parties  to that  certain  Credit
Agreement  dated as of May 12, 2000, as amended by that certain First  Amendment
to Credit  Agreement  dated as of August 4, 2000,  as  amended  by that  certain
Second  Amendment  to Credit  Agreement  dated as of  September  30, 2000 and as
further amended by that certain Third Amendment to Credit  Agreement dated as of
December 20, 2000 (as amended, the "Credit  Agreement").  Capitalized terms used
herein but not otherwise  defined have the respective  meanings assigned to them
in the Credit Agreement.

         B. The  Borrower has  requested  that the Lender (i) modify the rate of
interest applicable to the Facilities, (ii) apply a borrowing base limitation to
the Working Capital Revolving Credit Facility, (iii) extend the maturity date of
the Construction  Loan Facility,  (iv)  cross-collateralize  the Commercial Card
Purchase  Obligations  (as  hereinafter  defined)  with the  Obligations  of the
Borrower, and (v) otherwise modify certain covenants.

         C. The Lender has agreed to the foregoing changes, subject to the terms
and conditions set forth in this Amendment.

         NOW,  THEREFORE,  in  consideration  of the  premises  and  the  mutual
covenants  and  agreements  herein  contained,  and for other good and  valuable
consideration,  the receipt and adequacy of which are hereby  acknowledged,  the
parties hereby amend the Credit  Agreement,  effective as of the Effective Date,
as follows:

1.       INCREASE OF INTEREST APPLICABLE TO THE FACILITIES.  As of the Effective
Date,  the  formula  used in  computing  the  interest  rate  applicable  to the
Facilities  will  be  changed  so  that  the  interest  rate  applicable  to all
Facilities  will be equal to the Prime Rate,  plus three percent (3%) per annum.
Consequently,  the  Eurodollar  Rate will no longer  be  available  as a pricing
option for any Loans,  and the  Alternate  Base Rate will be modified  solely to
include a reference to the Prime Rate, and the  Applicable  Margin will be fixed
at  3.00%.  As a result,  as of the  Effective  Date all of the Loans  will bear
interest  at a rate of  Prime  Rate  plus  3.00%.  In order  to  effectuate  the
foregoing,  the  definitions of the terms  "Eurodollar  Base Rate,"  "Eurodollar
Loan," and "Eurodollar  Rate," together with all references to such terms in the
Credit  Agreement,  are deleted in their  entirety as of the Effective  Date. In
addition,  the  definitions of the terms  "Alternate  Base Rate" and "Applicable
Margin" appearing in Section 1.1 of the Credit Agreement are amended as follows:

         "Alternate  Base Rate" means,  for any day, a rate of interest equal to
the Prime Rate for such day.


                                       21
<PAGE>

         "Applicable  Margin"  means,  with  respect to Loans of any Type at any
time, an interest rate per annum of three percent (3.00%).

2.       APPLICATION  OF BORROWING  BASE. As of the Effective  Date, the parties
agree that the Working Capital  Revolving Credit Commitment will be subject to a
borrowing base  limitation  equal to  eighty-five  percent (85%) of the Eligible
Accounts (as hereafter defined). In order to effectuate the forgoing, the Credit
Agreement is amended in the following respects:

         A.  Additional  Definitions.  The  following  terms are hereby added to
Section 1.1 of the Credit Agreement:

                  "Accounts"   means  and   includes  all   accounts,   accounts
         receivable,  notes  receivable,  reimbursements  and  other  rights  to
         payment of the Borrower and its  Subsidiaries,  whether now existing or
         hereafter arising.

                  "Borrowing Base" means, as of any determination  date, the sum
         equal to eighty-five percent (85%) of Eligible Accounts.

                  "Borrowing Base Certificate" means a written certificate to be
         delivered by the Borrower pursuant to Section  6.1(xii),  substantially
         in the form of Exhibit F attached hereto.

                  "Eligible  Accounts" means, as of any determination  date, the
         aggregate  unpaid balance (net of interest,  finance charges and contra
         accounts) of Accounts (a) which arose from bona fide, outright sales of
         items of inventory or from the  performance of services by the Borrower
         and its Subsidiaries,  (b) if arising from sales of items of inventory,
         as to which the items of inventory  have been  delivered or shipped for
         delivery,  (c) which are based  upon  valid,  enforceable  and  legally
         binding  orders or contracts and invoiced in accordance  with the terms
         of such  orders or  contracts,  (d) for which the  account  debtors are
         unconditionally  obligated to make payment, and (e) in and to which the
         Bank has a valid and perfected first priority  security  interest.  The
         term shall exclude the following:

                  (i) Any Account  which is in dispute or as to which any of the
                  Borrower  or its  Subsidiaries  has  received  notice that the
                  account debtor claims right of rejection,  return, recoupment,
                  setoff, counterclaim,  deduction or defense to payment, to the
                  extent of the actual or asserted contra amount;

                  (ii) Any Account which is subject to any  assignment,  adverse
                  claim or Lien (except Permitted Liens);

                  (iii) Any Account which is evidenced by, or as to which any of
                  the Borrower or its Subsidiaries has received, a note, chattel
                  paper,  draft,  check, trade acceptance or other instrument in
                  payment thereof or obtained a judgment with respect thereto;


                                       22
<PAGE>

                  (iv)  Any  Account  as  to  which  the  account  debtor  is an
                  Affiliate of the Borrower;

                  (v)  Any  Account  as  to  which  the  account   debtor  is  a
                  Governmental Authority if the Bank is unable to obtain a valid
                  and  perfected  first  priority   security  interest  in  such
                  Account;

                  (vi) Any Account as to which the account debtor has died or is
                  the  subject  of  dissolution,   liquidation,  termination  of
                  existence,   insolvency,   business   failure,   receivership,
                  bankruptcy,  readjustment of debt,  assignment for the benefit
                  of creditors or similar proceedings;

                  (vii) Any Account which remains  unpaid for a period in excess
                  of two hundred  forty (240) days  beyond the  original  stated
                  invoice date that is due from any State Indemnity Fund Account
                  Debtor;

                  (viii)  All  Accounts  which are due from any State  Indemnity
                  Fund Account  Debtor who owes  Accounts  ten percent  (10%) or
                  more of which  remain  unpaid  for a period  in  excess of two
                  hundred  forty (240) days beyond the original  stated  invoice
                  date;

                  (ix) All Accounts which are due from any account debtor (other
                  than a State Indemnity Fund Account Debtor) who owes Accounts
                  ten percent (10%) or Fmore of which remain unpaid for a period
                  in excess of ninety (90) days beyond the original stated
                  invoice date;

                  (x) Any Account  which is due from an account  debtor who is a
                  Person not located in the United States or which is payable in
                  a  currency   other  than  U.S.   Dollars   (unless  the  Bank
                  determines,  in its sole  discretion,  to include such Account
                  and the Bank shall  have  first  received,  at its  option,  a
                  written  opinion in form and  substance,  and from counsel for
                  the Borrower,  satisfactory  to the Bank  reflecting  that all
                  necessary  steps have been taken to render the Bank's  Lien on
                  such  Account  properly  perfected  and of first  priority  or
                  backed by foreign credit insurance);

                  (xi) If the aggregate Accounts due from any account debtor
                  exceed twenty percent (20%) of the total Accounts outstanding
                  as of any determination date, the amount by which such
                  Accounts exceed twenty percent (20%) of the total Accounts;

                  (xii) Any Account that is a bonded account due from an account
                  debtor that is a contractor; and

                  (xiii)  Any  other  Account  as to  which  the Bank has made a
                  determination,  in the reasonable  exercise of its discretion,
                  that the prospects for collection are doubtful.


                                       23
<PAGE>

                  "State Indemnity Fund Account Debtor" means any account debtor
         of the Borrower or any of its Subsidiaries which is an entity,  fund or
         program that is subject to the Oklahoma  Petroleum  Storage Tank Reform
         Act (17 Okla. Stat. Secs. 321, et seq.).

         B.  Modification  of  Definition.  The definition of the following term
appearing  in Section 1.1 of the Credit  Agreement is amended in its entirety to
read as follows:

                           "Working Capital Revolving Credit  Commitment" means,
                  as of any  date  of  determination,  the  lesser  of:  (i) the
                  Borrowing   Base  as  of  such  date,  and  (ii)  the  sum  of
                  $6,500,000,  or such other amount to which the Working Capital
                  Revolving Credit  Commitment may be modified from time to time
                  pursuant  to  the  terms  hereof.  As  the  context  requires,
                  "Working Capital  Revolving Credit  Commitment" also refers to
                  the obligation of the Lender to make Working Capital Revolving
                  Loans and  issue  Facility  LC's  under  the  Working  Capital
                  Revolving Loan Facility.

         C. Borrowing Base  Certificate.  The Borrower  covenants to provide the
Lender a Borrowing  Base  Certificate on or before the 20th day of each calendar
month calculated as of the last day of the immediately preceding calendar month.
In order to effectuate  the foregoing,  as of the Effective  Date, the following
Section 6.1(xii) is hereby added to the Credit Agreement:

                  (xii) On or  before  the 20th day of each  calendar  month,  a
         Borrowing  Base  Certificate  signed by an  Authorized  Officer  of the
         Borrower  certifying as to the matters  involved in the  calculation of
         the Borrowing Base as of the end of the immediately  preceding calendar
         month.

3.       USE OF WORKING CAPITAL REVOLVING CREDIT FACILITY PROCEEDS.  The parties
hereby agree that proceeds from the Working  Capital  Revolving  Credit Facility
Proceeds  may no longer be used by the  Borrower  in any amount to  finance  the
Borrower's  purchase of shares of its capital stock from Patterson.  In order to
effectuate the foregoing,  the Credit Agreement is amended,  as of the Effective
Date, as follows:

         A. Section 2.2.1 Modification. Section 2.2.1 of the Credit Agreement is
modified as of the  Effective  Date by: (i) deleting in its entirety  subsection
(iv), and (ii)  correspondingly  inserting the appropriate  modifications to the
punctuation of that Section.

         B.  Section 6.2  Modification.  Section 6.2 of the Credit  Agreement is
modified as of the Effective  Date by deleting the  following  language from the
second paragraph of that Section: "; provided, however, that up to $1,000,000 of
the  proceeds  of a Working  Capital  Revolving  Loan may be used to finance the
Borrower's  purchase of shares of its capital stock,  as contemplated by Section
2.2.1(iv)". In all other respects, Section 6.2 shall remain unaltered.



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<PAGE>

4.       MODIFICATION OF CONSTRUCTION LOAN FACILITY.
         ------------------------------------------

         A. Extension of Maturity  Date. As of the Effective  Date, the maturity
date of all  outstanding  Construction  Loans and all other  unpaid  Obligations
arising  under or relating to the  Construction  Loan  Facility  will be due and
payable in full on August 10, 2001.

         B. Replacement  Construction Note. The Borrower agrees to make, execute
and  deliver to the Lender a  replacement  Construction  Note (the  "Replacement
Construction  Note"),  substantially  in the form  attached  hereto  as  Exhibit
"D-6B," in replacement of and substitution  for, but not in satisfaction or as a
novation of, the Construction  Note dated as of December 20, 2000,  delivered in
connection  with the  execution  and  delivery of the Third  Amendment to Credit
Agreement. The parties agree that, from and after the Effective Date, unless the
context  otherwise  requires:  (i) all  references  to the  "Construction  Note"
appearing  in the Credit  Agreement or any other Loan  Documents  shall mean and
refer to the Replacement  Construction Note, together with any and all renewals,
extensions  or  replacements  thereof,  amendments or  modifications  thereto or
substitutions  therefor,  and (ii) the term "Loan  Documents"  shall include the
Replacement Construction Note.

         C. Extension Fee. In consideration of the Lender's  agreement to extend
the Construction  Loan Facility,  the Borrower agrees to pay the Lender a fee of
$15,000.

         5.  CROSS-COLLATERALIZATION OF COMMERCIAL CARD PURCHASE FACILITY. As of
the Effective Date, any and all obligations and  Indebtedness  accrued under the
Commercial  Card  Purchase  Facility  (as such term is defined  below)  shall be
cross-collateralized  to the  Obligations  of the Borrower,  and shall enjoy the
same rights under the Collateral Documents as all other Loans made under Article
2 of the Credit Agreement.  The Borrower  acknowledges  that, as a result of the
amendment  to  the  definition  of  the  term  "Obligations"  effected  by  this
Amendment,  the prompt payment of all Commercial  Card Purchase  Obligations (as
such term is  defined  below)  will be secured  by a valid and  perfected  first
priority  security  interest  in all  of the  now  existing  and  after-acquired
tangible and  intangible  Property of the Borrower and each of its  Subsidiaries
and all  Collateral  Documents and will  guaranteed by the Guaranty  executed by
each of the  Subsidiaries.  In order to  effectuate  the  foregoing,  the Credit
Agreement is amended as of the date hereof in the following respects:

         A. New  Definitions.  The following  definitions  of  "Commercial  Card
Purchase  Facility" and "Commercial Card Purchase  Obligations" are hereby added
to Section 1.1 of the Credit Agreement (to be inserted in alphabetical order):

         (i)  "Commercial  Card Purchase  Facility"  means the  Commercial  Card
Purchase  Facility  established  by that  certain  agreement  entered into as of
August 21, 2000  between the Borrower  and the Lender  pursuant to which,  among
other things, the Lender agreed to provide a system to Borrower to process small
purchases  and reduce the need for the Borrower to process  vendor  invoices and
process checks.


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<PAGE>

                  (ii) "Commercial Card Purchase Obligations" of a Person means
         any and all obligations of such Person, whether absolute or contingent,
         now existing or hereafter created, arising or acquired (including all
         renewals, extensions and modifications thereof and substitutions
         therefor), under the Commercial Card Purchase Facility.

         B.  Amended  Definitions.  The  definitions  of the term  "Obligations"
appearing in Section 1.1 of the Credit  Agreement  is hereby  amended to include
the  "Commercial  Card  Purchase   Obligations."  In  order  to  effectuate  the
foregoing,  the definition of the term  "Obligations" is deleted in its entirety
from Section 1.1 of the Credit Agreement and replaced with the following:

"Obligations"  means  all  Commercial  Card  Purchase Obligations and all unpaid

                  principal of and accrued and unpaid interest on the Loans, all
                  accrued  and  unpaid  fees and all  expenses,  reimbursements,
                  indemnities  and  other  obligations  of the  Borrower  to the
                  Lender  or  any  indemnified  party  arising  under  the  Loan
                  Documents.

6.       CONDITIONS  PRECEDENT.  This Amendment shall become effective as of the
Effective  Date,  subject  to  the  Borrower's  satisfaction  of  the  following
conditions  precedent  (in  addition to the  conditions  precedent  set forth in
Article IV of the Credit Agreement):

         A.  Execution  of  Documents.   This  Amendment  and  the   Replacement
Construction  Note shall have been duly and  validly  authorized,  executed  and
delivered  to the Lender by the  Borrower,  and the  "Consent  of  Subsidiaries"
appearing after the Borrower's  signature to this Amendment shall have been duly
and validly authorized,  executed and delivered to the Lender by each Subsidiary
of the Borrower.

         B. Resolutions.  The Bank shall have received a copy of the resolutions
of the Board of Directors of the Borrower  authorizing  the execution,  delivery
and  performance  of this  Amendment,  the Credit  Agreement (as amended by this
Amendment) and the Replacement Construction Note.

         C. Accuracy of Representations and Warranties.  All representations and
warranties  made by the  Borrower  in the  Credit  Agreement  and the other Loan
Documents  and in Section 5 hereof  shall be true and  correct  in all  material
respects  as  of  the  Effective   Date  (except  to  the  extent  any  of  such
representations  and warranties  with respect to the financial  condition of the
Borrower refer to an earlier specified date).

         D. No Default.  There shall not have  occurred any Default or Unmatured
Default as of the Effective  Date,  and the Borrower shall be current in payment
of all  principal,  interest  and fees due and  owing  to the  Lender  as of the
Effective Date.

         E. Fee. The Borrower shall have paid the fee referred to in Section 2.C
above.

7.       REPRESENTATIONS  AND WARRANTIES.  All representations and warranties of
Borrower  contained in Article V of the Credit  Agreement  are hereby remade and
restated as the date hereof and shall survive the execution and delivery of this
Amendment. The Borrower further represents and warrants as follows:


                                       26
<PAGE>

         A.  Authority.  The Borrower has all requisite  power and authority and
has  been  duly  authorized  to  agree  to the  increase  in the  interest  rate
applicable to the Facilities,  the extension of the maturity of the Construction
Loan  Facility,  the  cross-collateralization  of the  Commercial  Card Purchase
Facility,  and to  execute,  deliver  and  perform  its  obligations  under this
Amendment,  the  Credit  Agreement  (as  amended  by  this  Amendment)  and  the
Replacement Construction Note.

         B. Binding  Obligations;  Enforceability.  This  Amendment,  the Credit
Agreement (as amended by this Amendment) and the Replacement  Construction  Note
are valid and  legally  binding  obligations  of the  Borrower,  enforceable  in
accordance  with  their  respective  terms,  except  as  limited  by  applicable
bankruptcy,  insolvency or other laws  affecting the  enforcement  of creditors'
rights generally.

         C. No Conflict;  Government Consent. Neither the execution and delivery
by the Borrower of this Amendment and the Replacement Construction Note, nor the
consummation  of the  transactions  herein  contemplated  or compliance with the
provisions  hereof and  thereof,  will  violate (i) any law,  rule,  regulation,
order, writ,  judgment,  injunction,  decree or award binding on the Borrower or
any of its Subsidiaries,  or (ii) the Borrower's or any Subsidiary's articles or
certificate of incorporation, partnership agreement, certificate of partnership,
articles  or  certificate  of  organization,  by-laws,  or  operating  or  other
management  agreement,  as the  case  may be,  or (iii)  the  provisions  of any
indenture,  instrument  or  agreement  to  which  the  Borrower  or  any  of its
Subsidiaries  is a party or is  subject,  or by which  it, or its  Property,  is
bound,  or conflict  with or constitute a default  thereunder,  or result in, or
require, the creation or imposition of any Lien in, of or on the Property of the
Borrower or any of its Subsidiaries pursuant to the terms of any such indenture,
instrument or agreement.  No order, consent,  adjudication,  approval,  license,
authorization,  or validation of, or filing,  recording or registration with, or
exemption by, or other action in respect of any  governmental  or public body or
authority,  or any  subdivision  thereof,  which  has not been  obtained  by the
Borrower or any of its Subsidiaries,  is required to be obtained by the Borrower
or any of its Subsidiaries in connection with the execution and delivery of this
Amendment, the borrowings and other credit extensions under the Credit Agreement
(as  amended  hereby),  the  payment  and  performance  by the  Borrower  of the
Obligations, or the legality, validity, binding effect or enforceability of this
Amendment,  the  Credit  Agreement  (as  amended  by  this  Amendment)  and  the
Replacement Construction Note.

         D. No Material  Adverse  Change.  Since March 31, 2001 (the date of the
latest  financial  statements of the Borrower  which have been  delivered to the
Lender), there has been no adverse change in the business, Property,  prospects,
condition  (financial or otherwise) or results of operations of the Borrower and
its  Subsidiaries  which could reasonably be expected to have a Material Adverse
Effect.


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<PAGE>

8.       MISCELLANEOUS.
         -------------

         A.  Effect  of  Amendment.   The  terms  of  this  Amendment  shall  be
incorporated  into and form a part of the Credit  Agreement.  Except as amended,
modified and supplemented by this Amendment,  the Credit Agreement and all other
Loan Documents  shall continue in full force and effect in accordance with their
original stated terms, all of which are hereby reaffirmed in every respect as of
the date hereof. In the event of any  irreconcilable  inconsistency  between the
terms of this Amendment and the terms of the Credit Agreement, the terms of this
Amendment shall control and govern,  and the agreements  shall be interpreted so
as to carry out and give full effect to the intent of this Amendment.

         B. References to Defined Terms. The parties  acknowledge and agree that
the terms  "Loans" and  "Obligations"  as used in the Credit  Agreement  and any
other Loan  Documents  will include all  Commercial  Card  Purchase  Obligations
outstanding under the Commercial Card Purchase Facility. Further, all references
to the "Credit Agreement" appearing in any of the Loan Documents shall hereafter
be  deemed  references  to  the  Credit  Agreement  as  amended,   modified  and
supplemented by this Amendment.

         C. Exhibits. The form of Replacement  Construction Note attached hereto
as Exhibit D-6B is hereby  substituted  for Exhibit D-6 to the Credit  Agreement
and incorporated therein by this reference.

         D.  Descriptive  Headings.  The  descriptive  headings  of the  several
sections of this  Amendment are inserted for  convenience  only and shall not be
used in the construction of the content of this Amendment.

         E.  Governing  Law. This  Amendment  shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the State of Oklahoma.

         F. Reimbursement of Expenses. The Borrower agrees to pay the reasonable
fees and  out-of-pocket  expenses  of Crowe & Dunlevy,  counsel  to the  Lender,
incurred  in  connection   with  the  preparation  of  this  Amendment  and  the
consummation of the transactions contemplated hereby.

         IN WITNESS  WHEREOF,  the  Borrower and the Lender have  executed  this
Agreement as of the date first above written.

                                  NESCO, INC.,
                                  an Oklahoma corporation

                                  By:   /s/ Larry G. Johnson
                                      ------------------------------------------
                                  Name:   Larry G. Johnson
                                  Title:  Vice President & Secretary-Treasurer

                                  BANK ONE, OKLAHOMA, N.A.,
                                  a national banking association

                                  By:   /s/ Tipton J. Burch
                                      ------------------------------------------
                                  Name:   Tipton J. Burch
                                  Title:  First Vice President


                                       28
<PAGE>

                                CONSTRUCTION NOTE


$8,000,000                                                        June ___, 2001


         NESCO, Inc., an Oklahoma corporation (the "Borrower"),  promises to pay
to the order of Bank One,  Oklahoma,  NA (the  "Lender"),  the aggregate  unpaid
principal  amount of all  Construction  Loans made by the Lender to the Borrower
pursuant to  Construction  Loan  Facility  established  under the  Agreement (as
hereinafter  defined),  in immediately available funds at the main office of the
Lender,  together  with  interest on the unpaid  principal  amount hereof at the
rates and on the dates set forth in the  Agreement.  The Borrower  shall pay the
principal of and accrued and unpaid interest on the  Construction  Loans in full
on August 10, 2001, and prior to maturity shall make such mandatory  payments as
are required to be made under the terms of Article II of the Agreement.

         The Lender shall,  and is hereby  authorized to, record on the schedule
attached  hereto,  or to otherwise record in accordance with its usual practice,
the date and  amount of each  Construction  Loan and the date and amount of each
principal payment hereunder.

         This Note is the Construction  Note issued pursuant to, and is entitled
to the benefits of, the Credit Agreement dated as of May 12, 2000, as amended by
the First  Amendment to Credit  Agreement dated as of August 4, 2000, as amended
by the Second  Amendment to Credit  Agreement dated as of September 30, 2000, as
amended by the Third Amendment to Credit Agreement dated as of December 20, 2000
and as further amended by the Fourth  Amendment to Credit Agreement of even date
herewith  (which,  as it may be further  amended or modified  and in effect from
time to time,  is herein called the  "Agreement"),  between the Borrower and the
Lender, to which Agreement reference is hereby made for a statement of the terms
and  conditions  governing this Note,  including the terms and conditions  under
which this Note may be prepaid or its maturity  date  accelerated.  This Note is
secured pursuant to the Collateral Documents, all as more specifically described
in the Agreement, and reference is made thereto for a statement of the terms and
provisions  thereof.  Capitalized  terms used herein and not  otherwise  defined
herein are used with the meanings attributed to them in the Agreement.


                                 NESCO, INC.,
                                 an Oklahoma corporation

                                 By:   /s/ Larry G. Johnson
                                     -------------------------------------------
                                 Name:    Larry G. Johnson
                                 Title:   Vice President & Secretary-Treasurer







                                       29