A knotted, round-top, hourglass-shaped steel wire coil. When laced together with cross-wire helicals, these coils form the simplest innerspring unit, also referred to as a Bonnell.
A knotted, round-top, hourglass-shaped steel wire coil. When laced together with cross-wire helicals, these coils form the simplest innerspring unit, also referred to as a Bonnell.