Originally Posted by Cheshirecatquilter

The four triangles you need to make square corners on this quilt measure 30/60/90. To get two outer edges for your quilt without a bias edge, measure from a line along the grain to make a 30 degree angle, and extend the triangle out long enough to make a seam across two of your diamonds, with the bias edge sewn to the diamonds. Two of these big triangles should be placed so their skinny end points, the 30 degree angle, meet at the point of one of your outer diamonds. Mirror this on the opposite side of your quilt, and you should end up with a rectangle.