L-plan castle

The evolution of its design was an expansion of the blockhouse or simple square tower from the Early Middle Ages.

A more compelling motivation for the L plan was the ability to defend the entrance door by providing covering fire from the adjacent walls.

For example, the stone walls of Muchalls Castle in Scotland are over 14 feet thick at the ground level.

A 17th-century reconstruction consisted of a probably equally tall structure, but one suited toward 17th century living and whose upper storey footprints mimicked the lower course.

Each of these towers, as well as a third structure destroyed by English and Spanish naval power, is an L-plan design.