different cats do like different things. Sisal is very popular with my cats. They also like carpeting. Besides the posts and trees that I have, I buy those small carpet squares and just lay them on the floor. They know that they can use those to scratch on. Outdoor kitties might liks a post of wood or bark covering (not as readily available, but they do make them). I've not tried this yet, but I know someone whos cat likes the kind that is made from layers of corregated cardboard and it sits horizontally on the floor. And then to encourage its use, rub catnip on in.