I have need to attach some notched things to a shelf.

This thing is a UClip, similar to this set of things: http://www.thingiverse.com/thing:5208

It has the standard Key on the edge of it, so that you can attach something, or a number of things to it by sliding the key into their notch.

1) Print a few of these
2) Attach them to flat things
3) Slide notched things onto them
4) Rejoice!