Introduction: Change the Bottom of the Shelf to a Little Tunnel
The shelf is also staircase for the cats to the cat runway which supported by two Ikea billy shelf.
Step 1: Ikea Stuva Storage Bench X 2
Cats would enter the toilet from the back
Step 2: Remove Back Board of the Drawer
Step 3: Put the Cat Toilet in It, Done
jimuncle made it!