A Bayonet Cap, often abbreviated to BC or B22, is a type of light bulb fitting that secures the bulb using two opposing pins which locate into slots within the lamp holder before being twisted into place. Developed in the late nineteenth century, the bayonet cap became the standard light fitting throughout the United Kingdom and many Commonwealth countries. Antique lighting professionally rewired for modern use is frequently fitted with B22 switched lamp holders, providing both authenticity and practicality while complying with modern electrical standards.