holes 10 and 11 39 the narrow weld seams 23 39 are provided on each side of the circular score line 22 as shown in fig1 on an enlarged scale in the case of the large pouring spout the upper wall portion 24 corresponds to area 24 39 in the case of the small circular openings 10 11 39 the area 24 39 being shown in fig1 in conjunction with the hole 10 and being here in any case a part of the upper triangular wall 8 from fig1 it may be seen however that the part 24 39 is also secured to the underlying welded part of the lower triangular wall 9 the reason for this joint is that after the weld seams 23 39 which provide the seal and are shown in fig1 on each side of the score 22 have been torn open the parts 24 24 39 still adhere thus in the case of the circular holes 10 11 39 the part 24 39 remains attached to the opposing triangular wall whereas the outer weld seam 23 39 which prevents leakage is separated the result is shown in fig6 in this case the air inlet 10 and the pouring spout 11 are both open these openings occur because in the case of the air inlet 10 the wall portion 24 39 continues to adhere to the lower triangular wall whereas in the case of the pouring spout 11 the area 24 continues to adhere to the upper triangular wall 8 thus the cross section shown in fig1 along the line b b in.