The “bench hook” (commonly referred to today as a “planing stop”) is an essential workholding feature on my bench. This L-shaped piece of iron is filed with teeth to bite into the end grain of the board to be planed. Peter Nicholson described it well in his 1812 book Mechanic’s Companion: “Near to the further or fore end A B [of the bench] is an upright rectangular prismatic pin a, made to slide stiffly in a mortise through the top. This pin is called the bench hook, which ought to be so tight as to be moved up or down only by a blow of a hammer or mallet. The use of the bench hook is to be keep the stuff [read: stock] steady, while the joiner, in the act of planing, presses it forward against the bench hook…. The bench hook is sometimes covered with an iron plate, the front edge of which is formed into sharp teeth for sticking fast in the end of the wood to be planed, in order to prevent it from slipping; or instead of a plate, nails are driven obliquely through the edge, and filed to form wedge-formed points.”
The above describes a slightly different style of hook than I have here. Mine is like Joseph Moxon's and Roubo’s. But this shows excerpt shows that there has always been a lot of variety.
The “pin” is seen under the bench next to the screw in the exact center of the photograph.
Here’s a quick tour of my main bench hook. The wooden shaft (Nicholson’s “pin”) is 1-3/8" x 2" x 7" in length. The exact sizing is not critical – it’s just a scrap I had laying around. The length just needs to be enough that you can reach it to whack it higher with a mallet when needed. My bench has a wide front apron, so I’ve got to reach quite a way to reach it.
But I rarely adjust the height. It’s almost always about 3/8" off the bench. If I keep adjusting it up and down, I will only wear the tight (“stiff”) fit in the bench’s top. A wobbly and loose hook is annoying in use. In reality, it is only when I am planing stock 3" or greater that I feel like raising the hook. Most every stock I work is fine with 3/8".
The teeth on my stop are spaced about 5 per inch. This seems to be pretty typical of the marks left on historic work. I’ve seen marks a little finer than 5 tpi, but don’t recall any much coarser. I like 5.
If you’re looking to install a bench hook, don’t be paralyzed with questions. It can be as cheap as a scrap of wood, or as awesome as a hand-forged and toothed iron hook. Just get the thing installed and adjust as needed.