Complex sentence: A keycard lock is a lock operated by a keycard, a flat, rectangular plastic card with identical dimensions to that of a credit card or American and EU driver's license which stores a physical or digital signature which the door mechanism accepts before disengaging the lock.
Split into simpler sentences: A keycard lock is a lock operated by a keycard, a flat, rectangular plastic card with identical dimensions to that of a credit card or American and EU driver's license. The card stores a physical or digital signature that the door mechanism accepts before disengaging the lock.