One of the force multipliers to successfully use gridfinity is the ability to make lots of boxes quickly with vase mode. All the multiple unit models I could find required printing the base of the box separately and gluing on later to be compatible with a gridfinity base grid. This model takes a different approach and “chains” the boxes together with a thin rib that continues to allow vase mode printing. Just clip the small rib at the base after printing and the chain can sit in any gridfinity base.

The rib may leave a gap if printing at 0.4mm width. Use a 0.6mm nozzle (or increase extrusion width) to close the gap and make vase mode walls like these a bit more robust.