A battery terminal puller is used to remove a battery clamp from a battery post. As a connection ages, the clamp and post can fuse together and become very difficult to separate.
A battery clamp puller is shaped somewhat like a diamond. There is a hinge at the top that allows the tool to open, and the hooks on the open end slip under the battery clamp. When the tool is tightened, a screw comes down from the hinge and presses against the post. The pressure builds on the hooks, and it separates the bond between the post and clamp.