fig1 preferably include a pair of arms for each wheel each of the clamping members 26 has frictional pads 28 positioned at the ends thereof to make frictional contact with the wheels 20 the wheels 20 which may be supported on hubs 34 through which pass the axles 32 are typically made of plastic rubber polyurethane or some other suitable material the length of the clamping members is such that the frictional pads 28 clamp the sides of the wheels 20 at a point that provides a secure frictional contact between the pads 28 and wheels 20 as seen in fig1 and 2 the contact position between the pads 28 and the wheels 20 may be midway between the hub 34 and the outer diameter edge of the wheel however any suitable position on the wheel surface that enables a frictional force sufficient to secure the wheel and preclude the wheel from rotating may be utilized as seen in detail in fig2 the pad 28 may be formed of two parts 280 and 282 the two parts include a resilient frictional pad 280 that contacts the wheel surface and a pad support 282 which may be metal plastic nylon or some other sufficiently strong material to support the pad 280 the two parts 280 and 282 may be glued together or.