When you have a pair of doors, they will lock into each other rather than into the frame like
single doors. There will be an active and an inactive door. The active door is the one with
the lock on it and is the one used most often in the pair. The inactive
door is the one that is usually stationary and only opened when the extra opening width is
required.
In some cases, both doors can be active. For example; a lot of schools will have
exit devices on both doors of a pair and one is used as much as the
other. Another example is double egress doors. In this case, both doors open in opposite
directions. One is usually used for entering while the other is used for exiting. In both
examples, there will sometimes be a center "mullion" (either welded onto the frame or the
removable type) so that the doors
will lock into this just as they would if it was a single door locking into the frame.
When you have an active and inactive door, the inactive of the pair will have to be secured in
some way so that when the active door locks into it, the inactive door cannot be pryed or pushed open
allowing unwanted entry. There are several different ways to achieve this, but the two most
common are flush bolts or surface bolts. Surface
bolts are mounted on the inside surface of the
door while flush bolts are mounted in the lock edge of the door and can't be seen when the
doors are closed. If you are using exit devices on both doors, then a surface vertical rod
device will keep the inactive door secure.
A pair of doors will sometimes have an "astragal" which covers the gap between the doors.
You can not use this astragal on a pair of doors that have both doors as active as the
astragal requires that the door it is mounted on be opened first...thus making the other door
inactive until this door is first opened.
We keep a complete stock of astragals and mullions with our doors and frames to make whatever
type of double door opening you might require.