Abstract: A timelock device comprising a mounting plate fixed at a location where the device is to be used, and a separate housing provided with a channel defining a passageway for the locking bolt of a door vault lock. The housing carries a locking pin, a timer and a mechanism operable by the timer means for moving the locking pin through the channel. Fastening means are used for detachably connecting the housing to the mounting plate. This device is particularly interesting since it allows for easy and accurate replacing of the operational parts of the device by replacement parts when the operational parts must be serviced.