a mounting assembly for connecting a light shelf to a structure in cantilever fashion . a pair of receiver units attach to the structure and each has a pair of brackets with a slot there between . a recess is formed on an upper interior surface of the upper bracket . the lower bracket has an abutment support surface distal to the structure . a pair of inserter units attach to opposite sides of the shelf , each having an insertion leg and an abutment support . the insertion leg inserts into the recess of a corresponding receiver when the abutment support rests on the abutment surface . the weight of the shelf pulls the abutment support into engagement with the abutment surface and pushes the insertion leg into engagement with the recess , holding the shelf horizontally .