Plates are disc weights that are slid onto the outer portions of equipment such as barbells and dumbbells to increase their overall weight. These plates are then secured to the equipment using collars to ensure that they do not slide off the apparatus.
A dumbbell is a weight training equipment usually consisting of a short rod with weights - usually plates and sometimes spheres - affixed on either end. The rod is often engraved with a cross-hatch knurl to improve grip. Dumbbells can either be used individually or in pairs.
A standard barbell is a wide steel bar which has weights, usually in the form of plates, affixed to either end. The central span of the rod is kept open for the hands of the lifter while the plates are added to either end. The weights are secured using a pair of collars which prevent them from sliding off. Cross-hatched knurls decorating the central portion provide grip on an otherwise smooth and slippery surface.
