My son is not very good at tying his shoe laces, so I made him this thing instead. It's basically a well known device from shoes, jackets etc, that are apparently called toggles (thanks). It could be redesigned in all sorts of ways, maybe even showing a head or some other object. This was made quite quickly, since he didn't want to wear his shoes on the way to kinder garten. :-)

I have made another version and have added the STL files for this also. It's called toggles.stl. This one is smaller and has a slightly different shape.

Print. Put a spring into the hole of the biggest thing. Put the smallest thing into it. Press it in, and put the shoe laces through the hole on the side, through both things. Finished.