Initially towers were open on the inside, but later the back was built and provided extra accommodation. Towers were rectangular or hexagonal, but master masons found round towers more stable, especially since a major technique in attacking a castle was to undermine the walls or towers. Providing more defences was no good if the towers could be undermined and toppled. Some castles had D-shaped towers built onto the existing walls.
|Arrow loops Caernarfon Castle (geographia.co.uk)|
Plantagenet arrow loops had a horizontal bar half way up, making the shape of a cross, which gave a wider field of vision. There was often a step below the loop for the crossbowmen to put their foot on to give them a steadier aim.
[adapted from The Medieval Castle Haynes Manual by Charles Phillips]
Ann Marie Thomas is the author of four medieval history books, a surprisingly cheerful poetry collection about her 2010 stroke, and the science fiction series Flight of the Kestrel. Book one, Intruders, and book two Alien Secrets, are out now. Follow her at http://eepurl.com/bbOsyz