This is a 1x1 Gridfinity bin designed to hold rulers, compatible with Zack's Gridfinity system. The rulers are held vertically to minimize the footprint. The bin is stable despite the height when attached with magnets, although bumping into the top of the rulers will cause it to be knocked over.
The rulers in the picture are the 4 pack Mr. Pen Machinist Rulers (6, 8, 12, 14 inches) (affiliate link). These are very affordable, and the different sizes give you flexibility when you need to get a ruler into a tight spot. They have both metric and imperial measurements. Other rulers may also fit, especially if you adjust the slots. See the “Source” section below.
The ruler slots have tapered edges to make it easier to slide the rulers in. The rulers are laid out at an angle in a staggered layout, which makes it easy to grab the middle rulers while keeping the footprint compact.
The bottom has 6x2mm magnet holes, courtesy of Gridfinity Rebuilt. These have a special design to assist with bridging, so the magnet holes print cleanly.
The print in the pictures was made with:
Source file is available here if you'd like to adjust something, like the size of the slots or their number. It wasn't really coded with customizability in mind so you may need to tinker a bit. It depends on Gridfinity Rebuilt in OpenSCAD, either clone the whole repository recursively (it's included as a submodule) or download the files yourself and adjust the file path in the first line.
The author marked this model as their own original creation.