23. Permanent erections. — Poops, bridge houses, pilot houses,
steering screens, or other permanent erections, entirely or partially
open at sides or ends or with one or more openings in the siaes, encis
or in the covering deck, and not fitted with doors, hatches, or other
means of closing mem, or which may not be easily closed in, shall not
be included in me gross tonnage, except when the spaces therein are
available or actually fitted or used for car^o, stores, passengers, or
crew, when they must be mieasured and form a part of the gross
tonnage of the ship. This section must not be confounded with that

{)ortion of the rules referring to shelter or awning decks or to deck
oads.
24. Open-deck spaces for berthing. — Spaces under shelter
decks, such as those imder bridges, etc., which are not inclosed or
readily inclosed, but are fitted with hammock hooks for berthing
accommodations, shall not form a portion of the gross tonnage.
25. Deck erections — ^Dimensions to framing. — In all cases the
interior dimensions of deck spaces and erections shall be taken to
the ceiling where such exists, but in the absence thereof, to the
interior edge of the frames or supports for the walls of these spaces.
Stiffeners on bulkheads shall be considered as supports, even though
not connected to the beam above or deck below.
26. Deck erections of irregular form. — ^When deck spaces
have irregular form, such that the general formula, indicated for the
measuring of deck spaces, can not be apphed to give correct results,
the spaces should be subdivided into smaller portions, and each oi
these measured by the most convenient geometrical formula adapted
thereto.
