One reference I found says 'nails for bellows' are 'scupper nails'.
-The Sailor's Word - 1867-
SCUPPER-HOSE. A canvas leathern pipe or tube nailed round the
outside of the scuppers of the lower decks, which prevents the water from
discolouring the ship's sides.
SCUPPER-LEATHER. A flap-valve nailed over a scupper-hole, serving
to keep water from getting in, yet letting it out.
SCUPPER-NAILS. Short nails with very broad flat heads, used to nail
the flaps of the scuppers, so as to retain the hose under them: they are
also used for battening tarpaulins and other general purposes.
SCUPPER-PLUGS. Are used to close the scuppers inboard.
SCUPPERS. Round apertures cut through the water ways and sides of a
ship at proper distances, and lined with metal, in order to carry the water
off the deck into the sea.