[Safe cheap way to keep cat from escaping my back yard.] ** Do you have a regular, domestic cat? If it's not an exotic; those spaces of galanized wire on top of the fence an average cat could slip thru in no time.Just sayin.
Use painted PVC held loosely on smaller pipes between brackets so they roll. Cats can't get their claws into the rolling plastic nor fit between the poles. Mount vertically instead of slanted to prevent both in and out.