purchase is one in which a rope reeves through a single fixed block. It merely changes the direction of the rope. See whip. A double purchase (a) or double whip is made by reeving a rope through a single block, then through another single block, and making the end fast to the one it was first rove through. When used as a guntackle purchase, the standing-block a is made fast to a ring-bolt on the cheek of the gun-port, and the hook of the running-block is connected to an eye on one of