The bigger black piece is a blackside adjustable hemmer, and the small silver gizmo is a bias cutting gauge. You put it on your scissors, adjust the gauge to the size you need and cut bias strips. The strips are fed into the binder attachment to sew on the edge of your project. I have them for my Singer 66 but not for my featherweight. There are many YouTube videos showing you how to do this. The Featherweight shop also has tutorials.