Summary

A pair of these things interlock and resist torque. Like a Hirth joint... Exactly a Hirth joint?

I have call for 2x4 lumber to be "articulated" and hold a position. Print out 2 of these, glue them onto something, and the 2 things can be clamped firmly in position with a bolt which also serves as the pivot.

There are several mechanisms like this, but this one is fairly thin and moves fairly easily when the clamp is loosened.