Single Fold Bias Binder (40MM) Evolve BLE8 - Single Fold Bias Binder - 40mm (BLE8-S5) You will be pleased at how easily this one-step attachment works. Our binder will turn the top edge of unfolded bias binding under while allowing the lower edge to remain straight, enclosing the edge of the fabric. This foot was created for the Evolve and Coverstitch machines.