Bracing piece, back frame, and backlight system of flat panel display device

A back frame of a flat panel display device, wherein the back frame comprises at least two assembling pieces, the at least two assembling pieces being joined to form the back frame, the back frame further comprising a bracing piece, the bracing piece being of a multiple-stepped configuration and mounted to the assembling pieces;

• wherein the at least two assembling pieces comprise a plurality of primary assembling pieces, the primary assembling pieces are joined to form a main frame structure of the back frame, the primary assembling pieces comprising a first primary assembling piece and a second primary assembling piece, the first primary assembling piece having an end forming at least two joint sections that are arranged to space from each other in a lengthwise direction of the first primary assembling piece, each of the joint sections having a structure mating an end of the second primary assembling piece, the first primary assembling piece using one of the joint sections to join the corresponding end of the second primary assembling piece;
• and
• wherein the bracing piece comprises a first step surface and a plurality of second step surfaces that integrally formed at one end of the first step surface, the first step surface forming thereon at least one bump, the bump forming a mounting hole adapted to mount and support thereon an external component, the first step surface being of a different vertical level with respect to each of the second step surfaces, one of the assembling pieces being selectively mounted to one of the second step surfaces in order to selectively adjust a mounting height of the mounting hole and the external component with respect to the one of the assembling pieces.