This is a magnetic whiteboard marker holder for four pens. Whiteboard markers should be stored horizontally to prevent drying out. The center plate has space for custom logos or anything else you want to put there. See one example in the files.

Print on its back, some support is needed below the half-pipes. Inside the half-pipes, support should not be necessary. I used a 0.4mm nozzle and 0.2mm layer height. Glue in 15 4mm diameter 2mm thick magnets in the back. I made sure that they were all polarized the same way when putting them in, but I haven't tested whether it actually matters.

Depending on how smooth the whiteboard surface is and how strong your magnets are, the holder might not hold perfectly with 4 markers in it. You can just put it at the bottom of the board or use other whiteboard magnets to stabilize it, if you have those.