Caliper

v. measure thickness or diameter using calipers

n. instrument that measures thickness or diameter; metal brace (for a deformed leg); thickness, depth; part of the brake system in an automobile

A caliper (British spelling also calliper) is a device used to measure the distance between two symmetrically opposing sides. A caliper can be as simple as a compass with inward or outward-facing points. The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler.
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Cal·i·per or cal·li·per n. An instrument consisting essentially of two curved hinged legs, used to measure thickness and distances. [more]Caliper - Community and Resources

Noun
1. an instrument for measuring the distance between two points
(synonym) calipers, calliper, callipers
(hypernym) measuring instrument, measuring system, measuring device
(hyponym) inside caliper
(derivation) calliper
Verb
1. measure the diameter of something with calipers
(synonym) calliper
(hypernym) measure, mensurate, measure out
(derivation) calipers, calliper, callipers

= brake caliper.
Ex: Aside from the normal wear and replacement of brake pads, there is not much maintenance needed for brake calipers.