The only thing canine about a bench dog is that, in a sense, it’s like a tooth protruding from a jaw. A bench dog is a peg or post that, when positioned in an opening in a benchtop, serves as a fixing point for a workpiece. Dogs are most often used with a tail vise, with one dog set into the vise, and one into the benchtop. The vise is tightened to hold the wood tightly between the two dogs. A single dog can also be used when planing, but the user must then concentrate not only on the action of the plane but on maintaining balance so that the piece doesn’t shift during the planing process.
Bench dogs or stops, as they are also called, are made of wood, steel, or iron. They may be wedge-shaped or may have a wide, protruding lip at the top to hold the dog in place. Some commercially made wooden dogs have a metal spring attached to one side enabling the dog to be set at various heights. The protruding lip may be smooth or have a milled face (crosshatched like that of a framing hammer) or teeth cut into it.
Many woodworkers feel more comfortable using wooden dogs. Planes do slip, from time to time, and it only takes one collision between plane iron and metal dog to waste an hour’s working time, turning the woodworker back into a machinist, grinding and sharpening the nicked blade.
For more details on the use of bench dogs, watch the following video: