How to read welding gauges

Welding gauges are available for checking alignment, checking dimensions before welding, verifying weld dimensions, and
checking porosity of welds.
Some gauges are multipurpose or single purpose.
WG-1 HI-LO ® Welding Gage measures internal alignment of pipe after fit-up/ alignment. This cuts radiographic rejects. It measures internal misalignment of pipe before and after tacking. Measurements read in inch on one side and metric on the opposite side. The gauge measures internal mismatch of pipe wall, scribe lines, weld fillet and crown height. It satisfies fit-up codes ASME, ANSI, API & Military.