An Exhibit is used as an attachment to a contract, letter or other document.
Photocopies of documents can be used as an exhibit.  
Parties to a contract do not have to sign each exhibit, but many elect to do so.  When not signed, the parties often initial the bottom of each page to signify that it was included with the contract when signed.

When You Need It
-To attach lengthy information or information that is already typed in an existing document, rather than in the body of a contract or letter.
-To use to reference detailed lists, such as a list of locations or items to be sold.  

Getting Started
-Specifically state that the document is "incorporated by reference" and identify the exhibit with a heading so that it is clearly associated with the contract or letter.   This means the listed items are "in the contract" just as if they had been typed out in the contract itself.  
-Lawyers call this simple process "incorporation by reference".   For example, when including an exhibit list of personal items to be sold with a house, you would include in the contract:  "Seller agrees to sell certain personal property listed on the exhibit attached hereto and incorporated herein by this reference."  
-It is also helpful if the exhibit itself includes language to identify it as a part of the contract or other document.  For example, the heading on the exhibit would say: "Exhibit to Residential Real Estate Sale Contract dated July 23, 1995, John Jones - Buyer and Susan Simms - Seller".

When to Review and Revise 
-If the content of the exhibit changes.
-If the number or title of the exhibit changes.