Abstract: A wall type security box sized to fit between, and to be fixed to, adjacent studs in a wall opening. The box is locked by a lock device in the form of an elongated rod having a key cylinder on one end and screw threads on the other end. After closure of the security box's door, and by manually gripping a key in the lock device's key cylinder, the elongated rod is, first, extended through a grooved bore in the box's face wall on one side of the box's access opening, second, extended through a through bore in the door, and third, rotated into threaded relation with a threaded bore in the box's face wall on an opposite side of the access opening. Preferably these bores are all axially aligned one with the other when the door is closed. The key is then removed to extend the cylinder's spring loaded lugs into latching relation with axial grooves in the grooved bore below the access opening, thereby preventing further rotation of the elongated rod and locking the security box.