Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5351999.

These attach to the four corners of a pet crate/kennel to make them easier to slide on carpet or other floor surface. They snap onto the wires of the cage. You can make them slide even easier by putting some adhesive-baked felt on the underside.

This is my first attempt at using Fusion 360.

Edit: uploaded a version that has slots for some old casters I had