A jack plane is the general-purpose bench plane, used for general smoothing of the edges, sizing of wood and jointing edges. Jack planes are about 12-15 inches long, and the blade can have either a slightly circled edge for smoothing stock, or a curved edge for jointing stock.
In preparing stock, the jack plane is used after the scrub plane and before the jointer plane and smooth plane. The name is related to the saying "jack of all trades". Jack planes perform both the work of smooth planes and trying planes.
A jack plane came to be referred to as a "No. 5" plane or a "Bailey pattern No. 5," at the end of the 19th century. Prior to that, all but the blade was made of wood in bench planes. The "No." nomenclature originally used by Stanley Tools to label its Bailey pattern plane products continues to identify planes made by various manufacturers. Not all manufacturers of the era had the same number scheme for their planes. Millers Fall and Sargent had different numbers to refer to the same planes. The jack plane is used to smooth off pieces of timber or lumber.