Dual Function Fold Binder Brother, SA231CVThe Dual Function Fold Binder is used to fold 1. 25 inch (32mm) wide bias fabric tape into 0. 31 inch (8mm) wide double fold bias tape, and then apply the bias tape binding to the edge of fabric. Attach the binder to the cover stitch machine simply with the two included screws. This accessory may also be used as a binder for single fold bias tape. For Use With: CV3440, CV3550