A "rider" is a legal term referring to a separate document with additional terms that are subsequent to the original contract. Riders can be used to make changes or add details. They can be found in any contract, from insurance to performance, that requires an addendum. Riders are typically written after the original contract is signed, and are referenced in the original to identify what they are modifying.
Incorporate the rider into the contract. In the introductory paragraph, state that the document is a rider, or addendum, to an existing contract. List the parties and date of the contract.
Add any additional terms to the contract into the body of the rider. The contents of the contract rider change or add new terms to an existing contract.
Sign the contract rider. Both parties must sign to show their consent to the additional, or different, contract terms.