"Coyote roller" seems a perfect name. Not only does it keep pets in the yard, it discourages coyotes from entering the yard.

Here in SoCal suburban sprawl is continuously encroaching on coyote habitat and they have taken to hunting and killing household pets. Both of my daughters live in areas where they've been seen stalking in broad daylight. The dry canyons near us are havens for them and there have been numerous instances of pet dogs and cats disappearing.

I've never seen a coyote roller installed on a fence but it certainly seems like something salable in this area. Of course, guys like us would just build our own but the millennials here can't even hammer in a screw successfully.