triangular compasses

Compa es having three legs, two opening in the usual manner, and the third turning round an extension of the central pin of the other two, besides having a motion on its own central joint. By this instrument three points may be taken off at once, and it is very useful in constructing maps and charts. triangular-crabs, s. pl. Zool .: A popular name for the family Maiade (q. v.), from the shape of the carapace. triangular-file, s . The ordinary, tapering handsaw file of triangular cro section. Also known as a three-square file.