Straight and 35mm arc fence. Our Singer sewing machine #4452 has two m4 .7 screws holding down the bobbin cover. Remove one screw and install either left or right side. Your machine may need a different thread on the thumb screw so verify and adapt before installing. I used “PLA Tough” for this build as the screw is small and the use is harsh. The risk of breaking is high so only attempt if you're prepared to recover from that failure.