Bunk Bed Cup Holders

Bunk bed cup holders for my kids because their cups would always get pushed off the edge. The first design ("B") is in two pieces for strength; I used super glue and M3 screws (I actually measured it to fit M4 but made it too small; I think you could fit M4 in there by heating the nut and pushing it in).
First design ("B") does not need support but the second one ("R") (with horizontal bracket) does.