Gully

[Jib]

Was a "gully" just any old knife or one with a folding blade?

[PirateQueen]

I think it's any very large knife, and there were ones that folded into the handle.

[Dorian Lasseter]

Google it...

Typical folding knife used throughout the 17th Century and into the 19th Century. Folding knives had the advantage of taking up less space and could be carried in a pocket without a sheath. Pocket knives proved popular among sailors and eventually evolved into more elaborate pocket knives containing other utensils, typically a scaling blade, and marlinespike, and still later such items as cork-screws and even tooth picks and screw drivers.