The width of a yan ling dao (雁翎刀) is almost constant except at the head of the sword and at the tip, which narrows sharply. The body of the blade is almost straight but curves slightly at the tip, and the handle is straight.
Niu wei dao (牛味道), or oxtail sword blades widen gradually from the base to the tip. The widest part of the tip can be about twice as wide as the base. The blade is curved.
Yao dao (腰刀), or waist words, so-called because they were worn on the waist, were common during the Qing dynasty (1644-1911 AD)