Abstract: A detachable lamp assembly for temporary installation in the existing electrical socket at the rear of the first trailer in a dual-trailer truck coupled to a tractor cab. The lamp assembly is energized when the headlamps of the tractor are lighted, and illuminates the forward end of the second trailer for coupling and uncoupling the first and second trailer in the usual low-level light conditions at night in trucking yards. Thus utilized, the lamp assembly is a useful aid in preventing breakage or damage of the vulnerable air connectors, and other adjacent parts, which damage commonly occurs when the driver cannot visually monitor the coupling or uncoupling operation.