On this is built the centre vertical keel, which is constructed of plates to form a continuous girder of 'I' cross-section and whose height usually determines the depth of the double bottoms .
Koku kokhiwe isiseko senqanawa esime nkqo, esakhiwe zizigqumi ekwenzeni izixhasi eziqhubekayo zecandelo elinqamlezayo loku-'I' elinobunzima obudla ngokubonisa ubunzulu bemiphantsi ephindaphindeneyo.