Keys. Two metal keys attached to a key ring. The key at centre left is a Yale-type key. The key at lower left uses a Chubb design. These two types of keys are commonly used to secure household doors, with the Yale key operating a spring-mounted lock that clicks shut when the door is shut, avoiding the need to lock the door. A Chubb lock has to be manually locked, usually to provide extra security in addition to the Yale lock. Another difference is that Yale locks usually have an internal latch, allowing them to be opened from the inside without a key, whereas a key is needed to unlock a Chubb lock from the inside. The Chubb (lever-tumbler) lock was patented in 1818. The Yale (pin-tumbler) lock was patented in 1861.