Replacement buttons are becoming increasingly difficult to find. You can buy a cheap hammer for less than a pen. But if you have a favorite hammer, a new handle will do. They must be tailored to the individual head, but must add years to life. If you've never changed a pencil before, you should put your head down, hold your head down, take another hammer, and bang the end of the handle over and over again. The head will bounce harder and harder. Trim the excess off the top of the handle and hammer in the wedges.