A jack plane is the general-purpose bench plane, used for general smoothing of the edges, sizing of timber but only making it smaller to correct size – wood edge jointing. Jack planes are about 12–15 inches long, and the blade can have either a slightly curved edge for smoothing stock, or a straight edge for jointing stock.
In preparing stock, the jack plane is used after the scrub plane and before the jointer plane and smoothing plane. The name is related to the saying "jack of all trades" as jack planes can be made to perform some of the work of both smoothing and jointer planes, especially on smaller pieces of work.
Early planes were all wood, except for the cutter, or combined a wood base with a metal blade holder and adjustment system on top. Although there were earlier all-metal planes, Leonard Bailey patented a number of all-metal planes and improvements in the late 19th century. 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. 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 used different numbers to refer to the same planes.