Holes to receive these stops or clamps are typically drilled in line with a vise in 3-4" intervals, with others added to the benchtop to serve various purposes.
Probably the oldest and most basic method of holding the work is a bench dog, which in its simplest form is simply a peg or small piece of wood or metal wedged into a hole in the bench top that stands just above the surface, allowing a workpiece to be clamped between it and an adjustable dog on a face vise.
Its shank is slid loosely into a “dog” hole in the bench until the tip of its hook touches the work.
It is set by hitting its top with a mallet or hammer, which causes the shaft to wedge tightly against the sides of the hole.
In addition to dog holes some workbenches have hardpoints, which are metal threads embedded in the wood.
Benches may also be made from plywood and Masonite or hardboard, and bases of treated pine and even steel.