Šajkača cap is easily recognisable by its design; the top looks like the letter V or like the bottom of a boat (viewed from above). It was derived from the 18th-century military cap part of the uniform worn by the Šajkaši, river troops guarding Belgrade, Danube and Sava against the Ottoman Empire, during the 16th- to 19th centuries. It subsequently spread throughout the civilian population of central Serbia, and in the 19th century it became an official part of the Serbian military uniform.