draft gage

draft gage

[′draft ‚gāj]
(engineering)
A modified U-tube manometer used to measure draft of low gas heads, such as draft pressure in a furnace, or small differential pressures, for example, less than 2 inches (5 centimeters) of water.
A hydrostatic depth indicator, installed in the side of a vessel below the light load line, to indicate amount of submergence.