Felines, seemingly incorrigible scratchers, rake their claws over rough surfaces to both clean and hone them. But the raking motion also sheds the claws’ dead and dulled outer layers and helps exercise leg muscles. Just as importantly, scratching allows the cat to leave its calling card, a territory-marking scent released from the paw pads. Wild cats and domestic felines with access to the outdoors usually choose a tree or fence for these purposes. Indoor cats, unless they are encouraged to use a scratching post, will opt for a piece of furniture or anything else that is stable, rough in texture and high enough off the ground to provide a good stretch.