Abstract: An attachment device (10) adapted for use with at least two retainers (14), the device (10) including at least two mountings (44), each for engagement with a retainer (14), wherein when a first one (14a) of the retainers is engaged with the device (10) it cannot be detached from the device until another retainer (14b) has been engaged with the device (10).

Abstract: A tightening system of straps for use in anti-skid and traction enhancement devices is disclosed. The tightening system comprises a central node which is located on the principle axis of the axle of a wheel and which has a plurality of extensions adapted to fasten a plurality of radially extending straps around its periphery. A plurality of radially extending flexible straps, which are attached to a surface contact member at their first 10 ends and to the central node at their second ends, are used to tighten the anti skid device. The flexible straps are passed through a buckle for tightening the surface contact members in the radial direction in order to eliminate outward bulging on the surface contact members as well as to avoid eccentricity in the strap system.