Porthole, port light, sidescuttle
A circular opening in the ship side to provide light and ventilation. A hinged metal cover or deadlight can be clamped over to secure in heavy weather.
Sidescuttles are divided into three types: Type A (Heavy), type B (Medium) and type C (Light). The minimum requirement for type A is that it shall withstand a water pressure head of 24m, 12m for type B and 6m for type C. Sidescuttles may be made for welding or bolting into the ship shell or bulkhead. They may be made with (type A and B) or without inside hinged deadlights (type C).