When building things with dowels and rods, I often want to connect one thing to another in a loose and easily configurable way. This thing is intended to go onto the end of a rod and give it a simple loop that can be connected to other things.

In the pictures here, I've connected a few on a "double split loop" (keyring). Then I put a few of these "vertices" together to form a tetrahedron. Using the same method, you could form any one of a number of structures. If you use a more rigid connection point than the keyring, you might be able to make a structure that is more solid.

Otherwise, it's just another thing in the Yazzo construction set.

1) Look at your construction project to see where you might be able to use such a thing.
2) Print a few of them out
3) Use them in your project

By default, they will fit on the end of a 5/16" rod.