A lock box useful to secure products in a display shelving system. The lock box is configured with first, second, third, and fourth quadrantal sub-frames that are combined into a rectangular frame unit. Each of the quadrantal sub-frames includes corresponding left-face and right-face quarter-panels, which adjustably and overlappingly and engage one another to form corresponding left and right sidewalls, which enables selectable adjustment of the height and depth of the frame unit. A hinge coupled along the front face of the frame unit, and a door that comprises an adjustable height first and second portion engages the hinge. A lock mechanism is disposed between the door and the frame unit to secure the door in a closed position.