Wikipedia
A bench hook is a workbench accessory used in woodworking, and its purpose is to provide a stop against which the piece of wood being worked can be firmly held, without having to use the vice, thus saving time. It makes handsawing safer and more accurate. This simple appliance (three sticks of wood) uses the force of the tool and gravity to hold the workpiece and helps guide the tool blade to keep the cuts right on the line. It also allows one to perform with ease (and safety) those cuts that would be terrifying on a power saw and which should be carefully avoided. The bench hook is simply a short wooden board with a batten fixed along the top edge (the stop), with another one - called the hook - fastened underneath the bottom at the opposite end (see diagram to the right). The correct practice is to have the stop shorter than the width of base and offset from one edge, thus allowing the saw to complete the cut without scarring the workbench surface. Left handers are obviously obliged to set the stop in reverse. In use the bench hook is laid flat over the bench, with the hook hard up against the front edge of same. With the workpiece thus firmly held against the stop, is easy to see that no clamps or other mechanical fixing are required, the wood being held in place by the combined pressure of the tool (a saw generally) and the hand.. Bench hooks are meant to be an aid commonly used with hand tools, such as the backsaw, a hand plane and, somewhat less frequently, a chisel of some kind. Although very simple to make, commercially made bench hooks have become increasingly available.