There are 3 versions, only 1 has been tested so far, thanks to Mr G for testing!

The print will sit on the 2 shoulders when put in touching the bottom left and the top right. When put in touching the top left and bottom right it will sit off the shoulders.

Seen in the photos is Milwaukee rectangular deep divider - big slot - v26, it has a long slot, it can be used both ways.

Milwaukee rectangular deep divider - no slot - v28 has no slot, it will only work when placed inside touching bottom left and top right.

Milwaukee rectangular deep divider - more precise slots - v29 should fit in both ways, it has reduced slots

Printing:

Best printed upside down with a brim. all walls is best.