Abstract: A device for preventing unauthorized opening of a door is disclosed comprising: a bracket for mounting against a side wall of a door; a brace connected to the bracket and having a ground engaging end and a lock end, the brace being biased into an unbraced position; and a release lever connected to the bracket and having a pedal surface and a lock surface; the device having in use a braced position in which the ground engaging end contacts a ground surface and the lock end of the brace is engaged by the lock surface of the release lever to prevent the brace from moving into the unbraced position, the release lever being biased into the braced position; the release lever being movable, by application of force against the pedal surface, into a disengaged position in which the lock surface disengages the lock end of the brace to allow the brace to move into the unbraced position.