Aside from the old fashioned mortise and tennon, or the longer tongue and groove, about the only way that craftsmen could join two boards together without hardware was to use dowels. Dowel joints were never precise, even though I have three different doweling jigs sitting on my shelf. But then one day along came the biscuit jointer to shove the dowel jigs right off the shelf.
The concept is simple but today dominates most standard cabinet making. A small fat saw blade, called often a wing cutter, is used to cut a curved slot in a board. Then an identical slot is cut in the mating board. Glue is inserted inside the slots with special glue bottles that apply the glue to both inside surfaces of the slot. Then a little wafer made of wood chips and called a biscuit is slipped into the slot and the joining board is slid on as well. The biscuit has the same curved shape as the slot it goes into. Everything is held together with clamps until it dries. One of the special characteristics of this method is that the biscuits go easily into the slots, but then swell up before the glue sets, making for a snug and strong fit. And of course, they come in all kinds of sizes. One other advantage is that there is no glue coming out of the joints between the two boards, no clean up, no staining problems. All the glue is on the side of the biscuits. A very important side effect to this is that you can now effectively glue together melamine sheets because the biscuits are gluing together the cores, not the plastic surfaces.
All that is missing is a special tool that looks like a grinder but is basically a jig for getting the slots in exactly the right place, in all circumstances. The Biscuit Jointer is in fact rather complicated, but once mastered, this becomes the essential tool for any cabinet shop.
If you are thinking about a really upscale present for the woodworker and you are not sure if he has one of these, simply look around the shop. If you don't find any of these oval shaped biscuits lying around or in his apron pockets, he doesn't have a Biscuit Jointer.