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.Initially I used Tinkercad to mix the two objects but it left some inner walls that messed with my print. I then imported it to Sketchup, cleaned the excess walls and lines and it came out perfect! I'm printing in a Afinia H printer with .20mm resolution and very little infill, I can't tell the percentage because Afinia's driver doesn't tells us how much it is.