Quarter Square Triangle (QST)

A quarter square triangle (QST) unit — also called an hourglass block — is made from four right triangles arranged so the straight grain runs along the outer edges of the finished square. To cut QST triangles, a square is cut on both diagonals (X cut), producing four triangles with the straight grain on the short sides. QSTs appear prominently in blocks like Flying Geese (traditionally made from two QSTs), Pinwheel, and Ohio Star. Because the outer edges are on the straight grain, QST units are more stable than HST units along the bias edges.