Answer: knurls

AnswerCrossword Clue
KNURLSThumbscrew ridges
KNURLSSmall ridges, as on a thumbscrew.
KNURLSKnots in wood
KNURLSCoin-edge ridges
knurlsknur
knurlssmall ridge or bead, esp. one of a series, as on a button for decoration or on the edge of a thumbscrew to assist in obtaining a firm grip
knurlsKNURL, to make grooves or ridges in
knurlsto make knurls or ridges on