Our square oak stool developed an annoying creak in two of its legs, resulting in a teardown & glue-up.
The legs come in pairs held in place by snug screw fittings:

The screw on the left slides into the tapered fitting on the right and latches firmly in place: no creaks in there! I have no idea what that fitting is called; my search-fu is unavailing.
In any event, the offending legs were loose enough to admit a 6 mil = 0.16 mm miniblind snippet shim:

Our Young Engineer, having taken up woodworking as a serious hobby, suggested the joint might have a loose dowel, which will be difficult to fix. Peering into the gap with a flashlight below showed that was the case:

While it might be possible to force the joint apart enough to properly re-glue the dowels, I opted for a half measure by applying a spreader and easing wood glue into the gaps using the shim:

An overnight session with the pipe clamp eliminated the creak, at least for now:

The blue-and-yellow clamp fixed the loose splinter you didn’t notice in the second picture.
Traces of glue along inside the joints suggest I’d done something like in the deep past. Ideally, I’ve learned enough to get it right this time.
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