Caponiers were added to four of the corners of the existing fort ( each with a stone staircase leading up to the top of the Redoubt ) .
Gunrooms were built alongside two of Caponiers to allow fire along the North and South - East Lines .
Caponiers were added to four of the corners of the existing fort ( each with a stone staircase leading up to the top of the Redoubt ) , and gunrooms were built alongside two of them to allow fire along the North and South - East Lines .