Caliper height gages
The basic design principles of vernier caliper gages are also applied in caliper height gages. The primary use of caliper height gages is in the field of surface plate work as a layout tool, for marking off vertical distances and for measuring height differences between steps at various levels.
Vernier height gages differ from caliper gages in that they have a single jaw, because the surface plate on which the instrument base rests functions as the reference plane. Vernier gages usually have offset jaws whose contact surfaces can be brought to coincide with the reference plane when the slide position indicates zero height.
The nonintegral reference plane requires great locating stability and internal rigidity from height gages in order to maintain a beam position that is substantially perpendicular to the surface plate. Consequently, with the exception of the less accurate models, vernier height gages are made with wide bases and with bars of strong cross-section; the bars carry the same kind of graduations found on the beams of vernier caliopers.
For marking off purposes, scribers can be attached to the contact jaw. These scribers are designed to have the edge substantially at equal level with the contact surface of the jaw, in order to make the height of the scribed line coincident with the dimension indicated by the gage.