The Tomu PCB has USB contacts on one side, but the other side contains components. The combined height may not be enough to keep the Tomu PCB inside the USB port.
Early revisions of Tomu used a piece of folded paper to keep the PCB secure. These cases were designed to alleviate this need.
The cases are designed in FreeCAD, and are distributed both in their source form and their production form.
This is the original case. It is a rectangle, and should work well.
This is a fancier case. It is designed to work with 0.8mm boards, and has a space cut out for the MCU. It has a lip on the end.
The Tomu 0.3 revision includes notches on the side for alignment with the PCB. This case is the same as tomu_0.2_case_fancy, but includes nubs to mate with the notches.
The Tomu 0.4 revision is 10mm wide, enabling more material on the side for stronger rigidity. Additionally, an alignment hole was added to the PCB, and this case has a corresponding peg. Guide rails were added to the sides to make it easier to fit into a USB slot.
A .STEP version of the Tomu case that was actually manufactured. This includes plastic snap tabs to hold the PCB in place, and makes it easier to remove from the slot.