Gauging is somewhat difficult for the beginner. The chief error is the tendency to put too much weight on the marking point and too little pressure of the sliding block on the face or edge. Such mistakes result in a crooked and irregular line, not at all parallel to the surface gauged from. A very light mark should at first be made, seeing that the block is pressed firmly and flatly on the surface gauged from, while the gauge should be slightly tilted to prevent the marker getting too deep into the wood. When a correct line has been formed, the depth can be readily increased so as to make it distinctly visible. In planing the rough part with the jack plane down to the gauge lines, occasional examinations should be made, in order to insure a regular approach to the lines, without going beyond at any point. The surfaces should be finished quite flat with the halflong to the centre of the gauge-lines, and the square blade may be applied occasionally to test the truth of each.

Modifications of the foregoing instructions will have to be made in cases when the conditions may be different, as, for instance, when the edges or ends do not require to be at right angles to the face. In such cases the sliding bevel, set at the required angle, would be used in a similar way to the square.