From CoMakingSpace Wiki
|Used with:||hand saws (Western style - push cutting),|
(hand tool area - under the old Hobelbank)
|Similar (More or Less):||shooting board|
A bench hook gives you a quick and easy stop to hold a workpiece when sawing by hand.
Basically it is just a board with two hooks: one at the underside that's pushed against the edge of the workbench, and one on top that you can then push workpieces against!
More information on Wikipedia!
A precisely angled (or adjustable) version of a bench hook is called shooting board and frequently used with planes.