Side Triangles

Side Triangles are placed along the edge of the quilt.  They are made by cutting a square from one corner to the opposite corner twice so that the straight of grain ends up along the edge of the quilt (this helps to keep the quilt from being distorted when it is quilted).  The size of the square is determined by multiplying the finished quilt block size by 1.414, adding 1.25"and then rounding up to the nearest 1/4".   For example, if the finished size of the blocks in the quilt is 10", the size of the square for the Side Triangle is (10" x 1.414) + 1.25" or 14.14" + 1.25" or 15.39" rounded up to 15.5".  Because we rounded up, the square will be just a little larger than it needs to be.  That's okay, cut the 15.5" square from corner to corner twice and when sewing the Side Triangles to the quilt blocks, let the excess stick out along the edge.  The edges can be trimmed once all the diagonal rows are pieced together.  

Corner
Triangles

Corner Triangles are placed at the four corners of the quilt.  They are made by cutting a square from one corner to the opposite corner (this time just once) so that the straight of grain ends up along the edges of the quilt (again, this helps to keep the quilt from being distorted when it is quilted).  The size of the square is determined by dividing the finished quilt block by 1.4.14, adding 7/8" and then rounding up to the nearest 1/4".  If the finished size of the blocks in the quilt is 10", the size of the square for the Corner Triangle is (10" / 1.414) + 7/8" or 7.07" + 7/8" or 7.94" rounded up to 8".