Abstract: Apparatus for securing an emergency exit door includes a bolt for engaging a keeper, a dogging mechanism for dogging the bolt and a fluid throttling device disposed between the bolt and dogging mechanism. An electrical timer is connected to the dogging mechanism by a solenoid and starts to count upon an attempt to open the door. After a predetermined time interval has run, the electrical timer releases the dogging mechanism and allows the door to open. If the electrical timer fails to release the dogging mechanism, the door will still open if pushed due to operation of the fluid throttling device, which slowly shortens under pressure, allowing the bolt to clear the keeper.In order to readily align the keeper with the bolt, the keeper is loosely mounted and guided into alignment with the bolt by a bevelled guide. Upon being latched by the bolt, the keeper is held rigidly between the guide and the bolt.