bez konteksta ovo je nagađanje i ne spada baš u brodogradnju (konstrukciju) nego u pribor, no možda slučajno pomogne...

čepovi na palubi za ulijevanje goriva, vode, ispumpavanje otpadne vode nazivaju se "plates" - deck fill plate, diesel plate, water plate, waste plate, i slično

Fuel System Fresh Water System
Fuel is filled through a fill plate on the deck. Don't confuse the fuel plate with the water and waste (i.e. pump-out) plates

The fresh water system (as opposed to the closed system
and the raw water system) is the system of potable water
on the boat. It is filled through a fill plate on the deck. Don't confuse
the water plate with the ones designated for waste (i.e.
pump-out) or fuel.
http://www.bananawind.us/PDF/Bareboat_Operations.pdf
http://beomarine.rs/motori.html#3

Tuš na krmi broda, ali i palubni čep spremnika za vodu, te pumpa i spremnik vode, što je sve na popisu standardne opreme, nalaze se u samom krmenom dijelu.
http://www.burzanautike.com/testovi/white-shark-225