PURPOSE: To fold the rest of cut parts to assemble a box, by arranging the folding lines in the order of l, a, l, b, l, a, l, b in the longitudinal direction of a rectangular plate with (a+b) in width, (2a+2b+4b) in length, when a box with the sides a, b, l is made, and a folding line with (a) in width is laterally provided and further, two cut parts from (a) width side, two cut parts from (b) width side, moreover two cut parts from (a) width side, and one cut part from (b) width side are provided up to the lateral foling line in turn along the vertical folded lines.

CONSTITUTION: A material is vertically folded along the line 1 with a width (a) as shown in the development of Fig. 2. Next, a cut line 2 is provided. A box can be completely assembled when the parts 3 are folded in turn. The satisfactory completion depends on the arranging method of respective sides of the front face, side faces, bottom of the box and the provition of cut parts for the purpose to appropriately move these faces to the necessary phases as a serial assembly. Respective faces are composed of two or more sheets as a folding allowance and hence, the strength is increased and well packed.