I have tried a lot of different feet, the plastic template for diagonals, etc. I'm back to my clear foot with red markings..I use that and have marked a scant 1/4" line & a center line with a sharpie from the very back of the machine bed, to the very front...these I covered with clear tape to keep it from rubbing off. Works for me. I can do the diagonal stitching to make half square triangles, etc. & have a constant seam allowance. I've marked this on all three of my domestic machines, using the same template for all of them...I took an index card, measured over the scant 1/4" and put the needle into the card to mark my spot. The lines on an index card are 1/4"...so my needle is just to the right of one of the lines in the card. I also marked the centers that way...putting the needle right in the line on the card...marked the front spot and a back spot...raised the needle and using the card...lined it up and used it as a "ruler" to mark the back to front (omitting the face plate). I also used the card with the needle in the scant 1/4" to mark the line for that back to front. No special tools needed.