Here is a couch spacer that I designed. You place these behind the back legs of a couch in case you want a space behind it for ventilation, or for curtains to drop behind the couch. Just easier to allow people to sit on the couch without worrying about it moving back and squishing anything behind the couch.

There are a few options I designed, but the third option (V3) is the one I found most appealing, especially because each side looked unique when placed down on the floor.