Belarius

The one catch is that the pin is often longer than the bulletin board's substrate, which can leave the thing you're trying to hold in place loose if you're avoiding puncturing it. You can see here that the earrings aren't flush - it's the pins that are anchoring things. Because the substrate on this board is so shallow (even more so than my old office), I've recently started using rubber o-rings, threaded like the earring is a kabob skewer, to both 'shorten' the length of the pin and to add a compressible cushion that helps keep items from sliding around.