As with most people, I have more tools than I have space to organize them, so I made these! Good strong cup magnets hold the wrenches up on the exterior of my upper toolbox.

The rectangular one is built to hold the Craftsman CMMT99441, but I am sure it would work for others. The rectangle is 23.5-mm wide and 16-mm deep. 

The round one is built to hold the TEKTON SRH01210, but I am sure that it would work for others. . The inner diameter is 20-mm.

They use #8-32 X ½-in flat-head screws and ¾-in cup magnets. 

The printed units shown in the photos are Hatchbox red ABS 0.35-mm layer height, 50% fill.

Material, layer height and fill percentage are flexible.

Support is required, brim is optional.