1. The compass generally used in slojd is a simple one made of steel with a hinge. As it is often necessary to maintain the distance between the arms unaltered, this compass is provided with a bow, which is attached to one arm, and which can be secured to the other by a screw. A compass of this kind is called a bow-compass (Fig. 24).

When segments of large circles have to be described, beam-compasses are used. In place of the arms of the ordinary compass, these are furnished with trammels, aa, united by a cross-piece or beam, b, and pointed at one end, where there is a steel pin. One of the trammels is fixed to the cross-piece; the other is movable, and is adjusted by means of a pin.

Fig. 23. Cutting Gauge. 1/4.

Fig. 24. Compasses. 1/4.

Fig. 25. Trammel Heads, or Beam Compasses. aa. Trammels, bb, Beam.

2. The Caliper Compass is used to measure the thickness of round or oval objects. This compass has very strong curved arms with points which taper obliquely. The ordinary caliper compass may be used to measure the diameter of a hole, by turning the arms round the hinge until the points are turned away from one another (Fig. 26).