Guide-bars are often made singly, and planed singly, for the convenience of an easy adjustment afterwards, when the friction surfaces of the bars and guide-blocks in contact are become worn. A guide-bar is easily held for planing, while in a vice or a vice-chuck, the vice or chuck being situated in any convenient place on the planing-table. A guide-bar may also be planed while held in contact with a face of an el-chuck, with four or five plates and bolts, in the position denoted in Fig. 740.

The face of a guide-bar is the upper surface while being planed, or that surface which is to be in contact with the guide-block or sfide; and at each end of the bar a shallow gap should exist below the face, after it is finished to its required dimensions. Such spaces are convenient both for planing, and to provide openings, into which the ends of the guide-block shall extend while in ordinary action. These spaces are formed at the time of casting, or if the bar is of forged steel, at the time of forging.