Standard plate casters have kingpins that securely join the casters' mounting plates to their frames. They are used in nearly every industry and are the most common type of caster used for general purpose applications. The casters' mounting plates install onto the bottom of machinery, carts, or other equipment, and the casters allow the equipment to roll to reduce effort when moving or repositioning it. These casters are available in swivel and rigid versions. The swivel casters can rotate 360°, allowing equipment to change directions while rolling. The rigid casters roll in a straight line. Two rigid plate casters will often be paired with two swivel casters to allow the equipment to both maneuver around curves and obstacles and maintain a straight course while rolling.