A LED lamp assembly for use in a long passage includes an elongated rectangular housing carrying multiple power-output electric connectors, a power-input electric connector and a power switch, a flat rectangular light source having a light-emitting face and selectively fastened to a rectangular top end of housing in one of four angular positions that spaced from one another at 90° angle, and a mounting plate extending perpendicularly from one side of the rectangular end wall of the housing having a plurality a plurality of equiangularly spaced and smoothly arched mounting slots for mounting.