Beam-Compass or Trammel Points.] [Illustration: Fig.209.Outside Calipers.] [Illustration: Fig.210.Inside Calipers.] The _marking-gage_, Fig.

211, consists of a head or block sliding on a beam or bar, to which it is fixed by means of a set-screw.

On the face of the head is a brass shoe to keep the face from wearing.

Projecting thru the beam is a steel spur or point, which should be filed to a flat, sharp edge, a little rounded and sharpened on the edge toward which the gage is to be moved, Fig.212.It should project about 1/8" from the beam.

If the spur be at all out of place, as it is likely to be, the graduations on a beam will be unreliable.