An angle gauge is a tool consisting of two arms which are at any desired angle to each other; consequently, the name of any particular gauge is the number of degrees of arc in the angle of the gauge. The gauge denoted by Fig. 292 is a hundred and twenty, because this is the quantity of degrees in the angle between the two arms. The tool denoted by the Figure is made of one piece, but, by making the two arms of distinct pieces, an instrument may be formed which is capable of adjustment to any angle. This is effected by connecting the two arms with a bolt, nut, and washer ; if thus fitted, the arms of the gauge may be made to subtend any angle by adjusting the arms to the angle-measurer shown by Fig. 293. During this adjustment the nut and bolt should be screwed tight, so that the arms cannot be shifted by any amount of proper handling; and while in this condition, the gauge is opened or closed by means of a wood hammer, or some other soft hammer. An angle gauge having adjustable arms should have one thick arm, corresponding to the pedestal of a square; and into one end of the thick arm a gap is formed for containing one end of the other thin arm of the gauge, termed the blade; and the two pieces are therefore united together by means of the joint bolt through both arms at the place of the joint-gap. A gauge thus made requires the thick arm to be put to the straight-edge of the angle measurer (Fig. 293) whenever it is necessary to adjust the arms to subtend the angle desired.