Cats are armed with razor-sharp claws that are hooked at the ends so that they
can get a good purchase on prey. They are normally kept retracted so that they
stay sharp, but when the paws are used to capture prey they are protracted out
of the flap of skin that covers them.
Claws grow continuously and, periodically, the old outer casing needs to be
removed to reveal the new, sharp claw underneath. This is done in strategic places
so as to leave scent messages.