Definitions for "Flush bolt"
n. a non-keyed deadbolt, with a one piece escutcheon/faceplate, typically mounted flush to door surfaces
A door bolt that is flush with the face or edge of the door. For use on a dummy door.
A bolt that is mortised into the edge of a door that will lock either or both the top and bottom of the door. Usually used on a pair of doors so that one door will remain closed or inactive, allowing the other door to lock into it.