This is a 2x3 Gridfinity bin for holding spools of thread. I use it for leatherworking, specifically to hold small spools of Ritza Tiger Thread, but it works for any standard size thread spool.

This model consists of a single cutout that holds six spools of thread and a rectangular cutout conveniently sized for an envelope of John James saddler needles.

This is a bit taller than it has to be to prevent spools from getting knocked out or unwinding, or to prevent a stray arm and/or hammer from clipping the needles and bending them.