The Yale lock was invented by Linus Yale Jr (1821-1868) between 1860 and 1868. His cylinder lock used pin-tumblers similar to those used in ancient Egyptian locks and had the advantage of using a very small key, capable of a great number of combinations. Consequently they are much used for front door locks. The Yale lock has a number of spring loaded pin tumblers, each in two parts, set in line with the key. The flat key is inserted and its serrated upper edge raises each pin to the correct height so that the inner cylinder can be turned.
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