Abstract: A lighting fixture including an elongated housing defining a downward open space of a uniform cross section shaped like a truncated cone and having two longitudinal upper tracks and two longitudinal lower tracks, a transparent, water-proof bottom board fastened to the lower track of the housing, a flat, elongated lamp holder made of hollow structure having two flat, longitudinal, lateral bearing walls fastened to the upper tracks for holding a respective lamp tube below, a flat, longitudinal, intermediate bearing wall for holding a lamp tube, and two opposite sloping walls bilaterally connected between the lateral bearing walls and the intermediate bearing wall, two end caps fastened to the housing at two opposite ends, and water sealing jackets fastened to two opposite ends of each lamp tube, wherein the lamp holder can be set in a first position with the intermediate bearing wall disposed at a higher elevation than the lateral bearing walls to hold a single lamp tube, or turned upside down and set in a seco