A small ridge or bead, especially one of a series, as on a button for decoration or on the edge of a thumb screw to assist in obtaining a firm grip. (Dictionary.com)
To impress with a series of fine ridges or serrations. (Collins Dictionary)
A small ridge, esp one of a series providing a rough surface that can be gripped. (Collins Dictionary)
Nurl face 3D cad library.
What nurl means?
To cut with reeding or fluting on the edge of, as coins, the heads of screws, etc.; to knurl