Half Square Triangle (HST)

A half square triangle (HST) is one of the most versatile units in quilting. It consists of two right triangles — each half of a square cut diagonally — sewn together along their long edges to form a two-tone square. HSTs appear in hundreds of traditional blocks including Ohio Star, Pinwheel, Birds in the Air, and Broken Dishes. Multiple efficient construction methods exist: the two-at-a-time method draws a diagonal line on the lighter square and sews on both sides; the eight-at-a-time method uses two layered squares to yield eight identical HSTs at once. After sewing, each HST must be pressed and trimmed to the exact finished size.