As a Forklift Operator I use a whiteboard a lot while at work to keep track of loads and lots, i'm forever loosing my dry erase markers until i taped a small magnet to them and they stick to my Forklift beside my seat, I wanted something more permanent so i designed and printed a set of these simple holders. I used 10mm diameter magnets extracted from a Dollar store Cellphone magnetic car vent mount and popped them into the base of the device and after a few iterations to get the thicknesses right to maximize the magnets pull and the strength of the plastic I settled on this as a final design. Print using supports for accuracy and use a very fine pair of needle nose pliers to pry out the support where the magnet will need to go.