Flat head pins were recommended for a Stack & Whack class I took years ago. I loved them and have used them ever since. The reason they were recommended was you can pin the fabric layers together and still lay your acrylic ruler on top of them to rotary cut. Of course you do have to make sure to keep the pins back from the edge you are cutting. Mine also don't melt if the iron gets too close. The machine sounds funny when you stitch through a flower but it didn't break the needle or hurt my Bernina. Whew!