The most typical of all the Dutch small ships was a tjalk (tjalka). The name of the ship came from the old Dutch language and firstly mentioned by N. Witsen in his work 'Architectura Navalis" (1690).
Tjalk was a flat-bottomed cargo ship with shallow draught and good qualities for use in the rivers and coastal waters of old Frislandia. Because of the flat bottom she was supplied by side sheet anchors. Mostly she was rigged with a removable mast. Only in the 19th century some of tjalks were provided with an additional small mizzenmast. The displacement of a tjalk was from 30 to 80 t. Besides the sprint mainsail the tjalk carried a sprint topsail, a fore staysail and a flying jib. By the beginning of the 19th century the sprint rigging of tjalks was often changed into usual for them gaff rigging, at that the main trysail was comparatively low with a short gaff and a very long boom.