This is an attachment for a nerf gun so that you can hold 72 nerf darts. It's in 3 pieces that you then superglue together since it was too big for my 3D printer. You need to print one piece of part A and two of part B.
I've also added a test piece to check the fit on the rail since I found I needed to scale mine up 115% to get it to fit better. So I would reccomend printing a couple of test brackets first to make sure it fits before doing the whole thing.