This device enabled the home-constructor to wind their own coils. It consists of a wooden bobbin with 46 metal spokes. The spokes are tapped into the bobbin in two layers, 23 spokes in each layer. Winding the coil involves creating a zig-zag pattern around the bobbin. The zig-zag advances eight spokes at a time, moving from one layer back to the other. This results in a 1 inch wide coil with a 2 inch core.

A coloured celluloid strip is included to finish off the outside edge of the coil.

When not in use, the spokes are stored inside the bobbin and sealed with a cork.

A scan of the instructions is shown opposite.