Note to Hamlet, 5.1.110: "pair of indentures"
pair of indentures: two copies of a contract, originally written on a single sheet of paper, which was then cut or torn along a serrated line, like a pair teeth, so that it could shown that the resulting "pair of indentures" belonged together. The sheet of paper used in making such a contracts was often quite large, large enough to wrap a skull in, so perhaps that is the source of Hamlet's comment about "the length and breadth of a pair of indentures."
Image Source: Kenneth Spencer Research Library