A tool used to unclog obstructions in drains and pipes is a plunger, also known as a force cup, plumber's friend, or plumber's aid. It comprises of a stick (shaft) that is often constructed of wood or plastic and a rubber suction cup. There is another bellows-like form that is more common and is made of plastic. Water in the pipe makes a plunger far more effective since it does not compress and transmits more force than air does. For difficult clogs, obstructions in the main line, or toilet clogs, a plumber's snake or chemical drain cleaner can be used in addition to a plunger when it is ineffectual.