close before the inactive leaf. This configuration is not recommended for high traffic locations. Center posts are an alternative to vertical rods at double door exits. This offers less clearance because the post remains in the middle when both doors are open. That said, the post can often be removed with a key for occasions when items larger than a single door need to pass through. Center posts may be preferred over vertical rods because they have fewer moving parts, thus they have fewer components that can break. Push bars themselves are some of the most reliable door opening mechanisms. To pass CE certification, bars must function between 100,000 and 500,000 opening cycles depending on the rating the manufacturer is seeking. Unlocking and latch hold In some applications, such as storefront entrances, panic bars may be dogged during business hours. Dogging is a common feature on panic bars in which the bar is retracted with a key—freeing the door to swing without latching. This allows customers to apply force to any portion of the door, not just the bar, in order to open it. Dogging is distinct from simple unlocking, which permits the user to open the door from both ends but still requires performing an action to release the latches. However, in applications where the exterior side contains an immovable dummy handle, as opposed to a knob or lever handle, it is usually impossible to unlock the crash bar without also dogging it. Dogging can extend the life of the bar. Some bars can be unlocked /dogged electronically, while others take a cylinder lock, hex key, or contain no key functionality at all. Dogging should be avoided in high wind areas where the door is susceptible to blowing open. Electric strike Unlike a traditional crash bar, this type contains a horizontal touch sensor and no moving parts. When the sensor is pressed, it releases an electromagnetic lock. It may be used in tandem with a motion sensor which unlocks for anyone who stands in front of the door. This type of release must still unlock in the event of a power failure, and in some jurisdictions, the door must automatically unlock for a fire alarm activation. Because these will not function in a long term power outage, they are most commonly used on secondary doors between a vestibule and the secure part of a building. On automatic doors In