Comprising of carefully machined and balanced cast iron wheel of about 20 cm in dia and 4.4cm thick, and steel spindle supported on the ball bearings in strong iron brackets. The sides of the wheel are red or grey painted. The top of wheel is chrome plated and is marked with a thick red line. A pointer is fixed to one of the brackets. Diametric hole is drilled in the shaft to take a pin and cord. The base is provided with four holes so that the apparatus can be fixed on a wall, complete with cord and hook.