Sorry can't photo at present. I found lining up the seams so the thread parts are in line Now using the fork pin I put them in parallel to the way you will stitch, put pin into the thread area and pull up a little further on.
I found I could sew almost up to the seam between the prongs .
If seam on a diagonal mark 1/4" seam allowance on open seam put one prong only into 1/4" place and line up on the other side with mark. Now tip and put second prong in don't look where just keeping fabric flat . Only one prong is in the correct place remember . Pull out gently as you reach the pin.
Hope you can understand will try to sort out photo later.