__ Line, Marker Seen on the Side of Ships
Puzzle 6 of The Moon Hard Pack
Question is: __ Line, Marker Seen on the Side of Ships
and the answer is: PLIMSOLL
Word Meaning:
PLIMSOLL — (UK, Ireland) A rubber-soled lace-up canvas shoe for sports or onboard ships; a precursor of trainers.
Definitions from Wiktionary.