Grooves cut into the walls of a cylinder making it a screw (positive) or a screw channel (negative). These structures guide the insertion and removal of a screw or bolt. Also, the act of inserting a screw or bolt into its receiving channel.
A thin piece of cotton, suture, etc.
Any thin filamentous structure (e.g., a stringy substance present in the urine in some infectious diseases of the urinary tract).