Warded lock

[1] During the Middle Ages they were used prolifically on monasteries where, because money and time were available, their complexity grew.

Warded locks are still in use today in the UK and Ireland for low-security applications, and on heritage sites such as ancient monuments and churches to preserve original features, with primary security being provided by other means such as a lever lock mechanism installed in addition.

In double-sided locksets (meaning locksets where the key can be inserted from either side of the door) the centre of the key shaft is solid and protrudes past the end of the bit, which slots into a hole on the opposite side of the lock.

When the correct key is inserted, it will clear the wards and rotate about the center post.

Due to the design of the lock, a well-designed skeleton key can be made to bypass the wards.

Keys for some types of warded locks often have a characteristic symmetrical shape. The one on the right is a skeleton key.
An old-style warded lock which is rim mounted to a door