I think waltherion did an excellent job when he designed this dart holder, I've printed one and the darts fit perfectly! It's easy to put then on the holder and to take them out. But they won't fall of by themselves.
But I needed a belt holder for my son and his friends, (we are planning a Nerf war party) so I needed a way to clip the holder on a belt, first I thought on designing a clip, but before I did that I searched Thingiverse for some belt clips. I found this glueable belt clip http://www.thingiverse.com/thing:30244
And mixed with the holder, I was worry that it might be a little too thin and frail but in the end I think it is strong enough for it's weight and for eight years old kids.
nerf_ammo_clip_4_belt_ver01_repair_skp.stl | 59.4KB |