A distance-gauge or height-gauge, is a piece of metal which serves as a kind of standard for adjusting the point of a planing-tool to a precise height above the planing-table, or to a precise height above a particular surface of an object being planed. The simplest and easiest to make of such gauges is merely a rectangular piece of sheet iron or steel, whose edges are smoothly filed to the desired dimensions. Such a gauge is used by standing it edgeways on the planing-table beneath the tool-point, and while the gauge is thus held square to the table with one hand of the operator, he uses the other hand to gently rotate the vertical traverse screw to advance the tool downwards until its point just lightly touches the upper surface of the gauge, at which time the tool-point is adjusted to the height required. Supposing it to be now necessary to plane an object so that its planed surface shall be at the same distance from the table as the height of the gauge, the horizontal traverse of the tool is put into operation after the tool-point is adjusted, and the planing effected. This planing will reduce the object so that its surface is at exactly the same height from the table as the height of the gauge. A distance-gauge is therefore a means of planing an object or a number of objects to a precise dimension without any necessity of measuring the objects with a calliper, or with any other gauge, until the objects are released from the machine. For a large quantity of work, no other gauge than a height-gauge can be used for measuring, while the objects are fixed to the table, because the undermost surfaces of the object or objects are frequently in close contact with the table-face, and therefore inaccessible to a measuring tool till released.

A superior class of height-gauges are represented by Figs. 724 and 725. These are preferable to sheet gauges, because they will stand on the table without being held. The one shown by Fig. 724 is a piece of round steel smoothly surfaced at both ends to the exact length required, the ends being also parallel to each other and at right angles to the length of the implement, to cause it to stand properly while in use. Fig. 725 denotes an ordinary right-angled block of three dimensions differing considerably from each other. Such a block serves as a distance-gauge, and is more useful for this purpose than a cylindrical gauge like Fig. 724, because the right-angular one represents three different dimensions. Either sort of these gauges are used by gently advancing the tool-point downwards, until it touches the gauge's plane surface, in the same manner as that mentioned for a sheet gauge.