Pitstone Windmill, an early 17th Century post mill

A post mill is a special type of windmill. The defining feature is that the building that houses the machinery is mounted on a single post. This gives the advantage over other designs of being easy to move the vanes into the wind, reducing the number of people needed to operate the mill to one.

Their design and usage peaked in the 1700s and 1800s, although many still exist today. They are primarily found in Northern Europe and Britain.