If you need to cut quarter-square triangles, our instructions will say something like this:
From purple print, cut:
2—5-1/4" squares, cutting each diagonally twice in an X for 8 small triangles total
First cut the squares the size specified. Then line up a ruler’s edge with opposite corners of a square. Cut along the ruler’s edge to cut the square in half diagonally, but do not separate the resulting two triangles. Instead, line up the ruler’s edge with the remaining corners and cut along the ruler’s edge to make four triangles total; separate the triangles. Because the triangles’ short edges are on the bias, avoid stretching them while piecing so you don’t distort the seams.