Cart has a different body structure for different purposes. Universal four-wheeled carts have a loading platform. Dedicated trolleys is structure range, some car system into box shaped, for handling weight light and easy handling of items; some body out Bay, easy placed rod, and axis and pipes, parts; some body shape completely and goods anastomosis, as gas bottle car; some is compact, can folding, easy carrying; some for easy handling barrels loaded liquid, and paper volume, tube-like goods, body shàng has two article flat steel formed low cant, to conducive to tube-like real rolled shàng rolled xià, as tube-like goods handling car. Modern trolleys are equipped with ball bearing wheels with solid tires or pneumatic tyres.