I love the fork shaped pins -- I use them and a drop of glue to hold the seams together. When I was learning to sew and until I got my computerized machines I never pulled the pins out. I never had a problem. However, hitting a pin with a computerized machine is a whole different kettle of fish. I try to pull out the pins unless they are holding something critical together. I did try to leave the fork pins in when sewing (I saw someone doing it on TV years ago) but my stitch length must have been different than the person on TV because the needle hit the edge of the second pin. No damage done, but I am not interested in taking a chance so I don't try to sew over them.