Heavy Duty Rail Mounted Clamping Window for sewing the left & right side panels on a cap without a driver. The CAP SIDE CLAMP is mounted directly to the machine drive bar (same as your cap driver), for a positive attachment. Machine specific adapters bolt to the clamp body and are used to attach and adjust the clamp to fit your embroidery machine. Hoop Tech makes adapter brackets for all major embroidery machine brands.