[Happy Monkey]

Ah, back to the jig. When in use, it was clamped in place, and the boards were clamped in position, but this is easier to see. The thick drill bit is for an insert which is essentially a steel cylinder with a threaded hole through it. A long bolt goes in where the thin drill bit is, and through the threaded hole in the insert. When tightened, the joint is pulled together.

I wanted this to be a "knockdown" bookcase which could come apart easily. Otherwise these joints would be dovetails with pins.