The jointer plane (also known as the try plane or trying plane) is a type of hand plane used primarily to straighten the edges of boards in the operation known as jointing. A jointer plane may also be used to flatten the face of a board. Its long length is designed to 'ride over' the undulations of an uneven surface, skimming off the peaks, gradually creating a flat surface.
Jointer planes are typically 20 to 24 inches (508mm to 610mm) long. There is also a shorter version of the jointer plane known as the fore plane which is around 18 inches (457mm) long.