Abstract: A patio door or sliding window security bar which is of the type that is normally stored parallel to a frame member of the opening and movable to a horizontal position braced against the sliding panel frame or jamb so that the sliding panel cannot be moved to give access through the opening. A bolt is fully contained within the hollow bar end and capable of being reciprocated through the medium of a barrel or cylinder that is installed into the lateral wall of the bar to enable the bolt to be moved into a socket formed in the sliding panel frame to lock the bar against being swung upward or downward. A locking arrangement including a keyway enables the bar to be locked in horizontal position by means of a removable key to prevent unauthorized opening of the patio door even from the interior of the building having the opening.