A cabinet includes four upright members having a triangular section and including two outer boards, an inner board, and two longitudinal groove formed at a joining portion of a first end of the inner board and an end of one outer board and at a joining portion of a second end of the inner board and an end of the other outer board respectively, the inner board including an upper first through hole and a lower second through hole; a plurality of board members each including four through holes at four corners respectively; a plurality of fastening devices at the through holes of the board members respectively, each fastening device including a hook assembly and a bolt and nut combination for securing the hook assembly, the upright member, and the board member together; and three board elements each disposed between the grooves of two adjacent upright members.