unbolt

verb (used with object)

1. to open (a door, window, etc.) by or as if by removing a bolt; unlock; unfasten.
2. to release, as by the removal of threaded bolts: He unscrewed the nuts and unbolted the inspection cover.

verb (used without object)

3. to become unbolted or unfastened.

verb (tr)

1. to unfasten a bolt of (a door)
2. to undo (the nut) on a bolt