The long bar or rod of a radius gauge for scribing and lining, is made of wood, if a light gauge easy to make is desired, and a couple of movable scribers are attached with small bolts having thumb-nuts. These bolts are moved along and carry the scribers along to any required part of the bar by means of a long slot which is nearly as long as the instrument. A wood gauge of this class is shown by Fig. 527, in which the scribers consist of straight wire that fits a hole in each bolt-head, so that by tightening the thumb-nuts the scribers are fixed. The mode of accurately adjusting the two points to any required distance from each other consists in first tightening the scribers with the nuts, and next gently hammering one of the scriber-heads until the point is gradually adjusted to its proper place. In the Figure, each scriber-head is denoted by H.