The tjasker (West Frisian: jasker, German: Fluttermühle) is a small type of windmill used solely for drainage purposes. It is distinctive for its simple construction, featuring only a single inclined shaft that carries the sails on one end and an Archimedes' screw on the other, in this way avoiding the need for any gearing.[1] The tjasker is commonly known as a typical Frisian windmill[2] though it is also found in other Dutch provinces and in north Germany.