Knurl is defined as a small projecting knob or ridge.
KT 1-3/8" knurled inside lock pin slides ups and down to lock or unlock the main door from inside the trailer. The pin is threaded into the mechanism by hand, requiring no tools. Refer to image #2 for a visual of placement.
Main Door KT Lock 380193 (no longer available) shown below.
Compatibility: 1970 - 1977 Airstream Trailers