I didn't finish the video I really wanted to do (on sculpting with polymer clay) so this is just a quick tip. It won't work for all tripods, but it should work for most of the ones that use hinges to tighten the legs.

This is my tripod and these plastic hinges have become lose over time and the way I have this hanging on my wall it needs to be able to bear a lot of weight without slipping. 

To tighten it what you can do is get some masking tape and just cut off a little strip…

…and stick it in the inside of the hinge right here.

The way this works is that there's a thicker area right there so that when you close it the joint tightens. But the plastic tends to wear down with time. So by putting the tape there you fill out the area more and make it tighter. There's only a small specific part where it's needed, but I use a whole strip so it doesn't move around to much.

With just one layer it might still slip so usually I put two strips just in case. That makes it almost

impossible to budge. The more strips you add of course, the more it tightens. Just be careful if, for example, you get the corner lifting like below. I usually redo these if it happens.

Over time the tape eventually wears down and tears along the spot that's tightest. It does leave a bit of residue sometimes but it's easy to clean with some alcohol.