Do you mean how to miter the border or your blocks? I use my degree ruler to miter the strips on my blocks. For the border, I fold the whole quilt on diagonal and extend the extra long border pieces out on a table. If I have more than 1 colour, I pin at each border intersection. I then take my degree ruler and draw the sewing line on the wrond side of the borders. I then stitch the border corner with big stitches on my machine (easy to remove). I open it up and make sure it is perfect, if it is, I restitch with regular sewing line. Then I trim the excess down to a 1/4 in. seam.