The Collaborative International Dictionary
Change key \Change key\ A key adapted to open only one of a set of locks; -- distinguished from a master key.
Wikipedia
A change key is a key on the lowest level of a master keying system. Change keys are also referred to as day keys. Typically change keys are issued to personnel that require access to one or two areas in a facility. By definition, a change key is not a master key.
Change key can also refer to the specialized keys used to change the combination setting of a combination lock.
Change key can refer to a special key on the "Sabre" Keyboard, located to the right of the "P" key, and can also be typed by doing ALT+0164, or using '@' in Turbo Sabre. Sabre is a Global Distribution System (GDS), used by travel agencies to book flights, hotel reservations, car rentals, etc.
Category:Locksmithing
Usage examples of "change key".
Already 'tis possible to walk the streets of New-York, passing among Buskers and Mongers, from one street-air to the next, and whistle along, and never have to change Key from B flat major.
But in telling his story he had too painfully relived the bitterness of that episode, and his narrative had been so much in the nature of a confession that he could not change key so readily.