Projecting towers allowed defenders to observe and fire along the outside of a town wall. Many were D-shaped and hollow, with no rear wall. They functioned as fighting platforms that could carry a movable wooden floor. A tower at Canterbury was fitted out this way again in 1940, reusing the medieval arrangement.
Notable Point · 5:17-5:42
Town-wall towers and Canterbury's 1940 reuse
Hollow towers let defenders cover the face of a town wall, and a Canterbury example returned to use with a movable wooden floor in 1940.