Assuming you are making a 9" block, then you want a half-square triangle that is 3" finished. You can do this by cutting 2 squares of fabric - one from the point colour, one from background colour. Cut each square 3-7/8". Draw a line diagonally across the background square. Layer the squares right side together. Now you will make 2 lines of stitching - sew 1/4" to the right of the diagonal line you drew. And then 1/4" to the left of it. Cut the square along the diagonal and press open. You now a have 2 (of the 4 you need) 1/2-square triangles for the friendship star.