surface of the workpiece to leave a shallow scratch on its surface.
Due to the nature of metal, and the accuracy generally sought after when machining it, a thick pencil or ink line would either be impossible to lay down accurately or prone to erasure during the machining operation. The crisp, bright mark exposed by the scratch of a scriber is semi-permanent and thin. The process of using the scriber is referred to as marking out and may require the addition of other hand tools and equipment.
Usually a layout stain of some form is used to increase the contrast between the scribed line and the background surface and is washed off with solvent on completion.
A scriber block is used to layout at a set height from the base, thus its second name surface height gauge or just "surface gauge".
The work piece is held against an angle plate so that it is perpendicular to the surface plate, the scriber block is then adjusted to the required height and used to scribe a line parallel with the table, by sliding the block along the table's surface.
The scriber block has pins that can be pushed to protrude through the base, these can then be used as limit pins to allow the block to press against the edge of the table, controlling its movement in that plane. The upright post can be adjusted to tilt back or forward, effectively moving the scriber point up or down in a controlled fashion, coarse adjustments are made by sliding the scriber along its clamping block.
The scriber block may also be used in place of a Dial Test Indicator to detect run out (a variation in concentricity) of a workpiece mounted in a 4 jaw chuck. The scriber point acts as a visual reference against which any variation in the work piece can be judged.