Test apparatus for either counting mesh or measuring irregular openings shall be compatible with the value of the tolerances.

Examples of test apparatus to count mesh include a counting glass and a standard metal rule .

Examples of test apparatus to measure openings include a graduated magnifying device, a vernier inside caliper, and a standard metal rule.

All test apparatus shall be calibrated against standards traceable to the National Institute of Standards and Technology

Counting Glass

Standard Metal Rule

Vernier Caliper

Micrometer