I have built a couple of kits, recently, that use this clever arrangement of tabs, slots, and a couple bits of cheap hardware to securely butt one panel against another at a right angle. One panel has a pair of rectangular ports with a round hole in between, and the other has a matching pair of tabs with a smaller T-shaped slot between. In use, the ports receive the tabs and a screw passes through the round hole and along the upright of the T to mate with a square nut captured in the arms of the T. There are many possible variations and the technique has lots to recommend it from a manufacturer’s standpoint, especially if you’re using a laser-cutter to make parts.
Now that I’ve noticed it, of course, I see it everywhere. Does anybody else remember the first time they noticed one, and what it was on? Does it have a common name?