I made this to complement the Gridfinity Aneng DMM holder

The four holes are there to hold either bare-ended probes or hooks. The probes do poke out the back so you won't be able to put another gridfinity widget behind it.

The bottom has cavities to glue in US (or Canadian) quarters to add some weight, lest the probes tip it over. If you use magnets with your gridfinity boxes, you probably don't need it.