Gauge

From MiddleWiki

1. A modern measure of the thickness of metal. Note that the smaller the number, the thicker the metal. By SCA regulations, all helmets must be of 16 gauge metal (.0598 inches/1.519mm), although 14 gauge or thicker is preferred for it's greater dent resistance.

2. A tool used by marshals to inspect armor. Available in a variety of shapes and sizes, they generally have at least two measurement abilities:

1. A 1 1/2" dowel (being that a helmet's grill or eyeslot cannot be constructed so that a dowel this diameter or larger can fit inside the helm)
2. A 1 1/4" recess to measure blade diameter (as no blade can be narrower than this)

Other tools may include all manner of hash marks, attachments and the like, resulting in some very odd looking instruments.