An indorsement is a signature of the holder typically on the back of a check.

Indorsement

The act of signing the back of a negotiable financial instrument, thereby making it payable to someone other than the named holder.

Signature

A person's name written in a distinctive way as a form of identification in authorizing a document.

Check

A written, dated, and signed instrument that directs a bank to pay a specific sum of money to the bearer or a designated entity from the drawer's account.