This is a clip for rescuing bees that get trapped in your windows. Poor things go towards the light so if your window doesn't open they can get trapped there trying to get out.

There are two versions: one that has a couple of hooks to allow you to use elastics to hold it closed, or the other where you can wind a spring using filament and a heat gun as shown. Print two copies of which ever version you wish and then both versions use filament as the pin that connects the two parts and you just use a lighter to heat the tip and fatten it so that it can't pull through.

The gap spacing is 4mm which is smaller than a queen excluder so worker bees can't escape. So it is similar to a queen clip, for holding a queen but they usually are spaced to keep the queen in, but allow workers to come and go.