improved, it became possible to construct a larger building footprint and a more complex shape than the simple blockhouse tower. A more compelling motivation for the L plan was the ability to defend the entrance door by providing covering fire from the adjacent walls. This stratagem was particularly driven by the advent of cannon used by attackers.

It was common for the union of the two wings to have very thick wall construction to support a major defensive tower in the union area. For example, the stone walls of Muchalls Castle