A method for installation of ceiling tiles in an improved mounting hook assembly to form a concealed grid system, the mounting hook assembly being attachable to a mounting stud (1) having recess on top portion to accommodate screws and fixed at the back of each tiles. The method includes attaching the mounting hook assembly to the tile; rotating a load bearing lever member; rotating a positioning lever member to position the load bearing member on a flange of a T grid bar; and fixing the tile below the T grid at a distance that is greater than the thickness of the tile so that when the tile is lifted up, the load bearing lever are returned to a position above the flange level of the T grid and any tile can be removed or installed in totally concealed grid system without dislocating tiles already laid.