Hey, I purchase these a couple years ago. I use them in my quilting classes for beginners. When my students are not sucessful at matching seams, such as a four patch intersections. You match the seams the same way as you do in hand piecing: by eye and using a straight pin if necessary. I also teach matching interlocking seams "by feeling" the higher ridge slide and lock...when you set the seams this was, you use these thin forked pins to pierce all the layers of fabrics at one time. the upper (pin) pins the top side of the interlocking seam, while the bottom pin pierces the lower sides of the interlocking seam. Thus when you sew down.....it forces the interlocking seams to stay put and you do not miss the seam (or points) by a thread or so...because it forces the pins to stay inside the two forked pins. Yes they bend very easily if you do not use them correctly. But they are a life saver for many of my students. Also, some of my students use them so the the backside of interlocking seams do not "flip-up" as you sew them. I hope this makes sense. If you buy them from a quilt shop, I am sure they would take the time to explain them to you! Good luck. Learning new techniques is always fun!