twin layers side wall 3 and the second edge 12 connects the forth edge 22 forming a second twin layers side wall 4 the fastening device using on the nested profiled components p is to ensure the two edges of the first twin layers side wall 3 and the second twin layers side wall 4 closely and firmly to connect with each other the fastening device comprises an unconventional bolt 5 and two nuts 6 which are respectively connected at two ends of the unconventional bolt 5 the unconventional bolt 5 comprises a main body 52 the cross section of which are in the shape of waist round or rectangular and threaded rods 51 respectively formed at the each end of the main body 52 the first cross section of the main body 52 has a center line defined by a longest diameter line of the first cross section that is perpendicular to a shortest diameter line of the first cross section and each end has a marking slot 511 the marking slot 511 has an opening aligned with the center line each nut 6 which can be either a hex nut or a square nut is screwed on the corresponding threaded rod 51 and a circular flake 61 is provided on the inner surface of each nut 6 to be formed into one single body the first twin layers side wall 3 is provided with a first through hole 31 and the second twin layers side wall 4 is provided with a second through hole 41 aligned with the first through hole 31 the first through hole 31 and the second through hole 41 having a shape and a size adapted to receive the noncircular cross section of the heads 521 of the unconventional.