noun
or in·den·tor -ˈdentə(r)
( -s )
Etymology: partly from indent (I) + -er or -or, partly from indent (III) + -er or -or
: one that indents:
a. usually indentor : one that orders by an indent (sense 2)
b. : an object (as of diamond, carbide, hard steel) having a pointed or rounded tip that is forcibly pressed against the surface of a metal so as to test for hardness and resistance to indentation