What does "indenture" mean?

Indenture: (Law) A mutual agreement in writing between two or more parties, whereof each party has usually a counterpart or duplicate; sometimes in the pl., a short form for indentures of apprenticeship, the contract by which a youth is bound apprentice to a master. The law is the best expositor of the gospel; they are like a pair of indentures: they answer in every part. C. Leslie. Note: Indentures were originally duplicates, laid together and intended by a notched cut or line, or else written on the same piece of parchment and separated by a notched line so that the two papers or parchments corresponded to each other. But indenting has gradually become a mere form, and is often neglected, while the writings or counterparts retain the name of indentures.