of the structural member provides torsional flexibility to the member with one end of the structural member 10 held rigidly the other end can be rotated about the long axis of the structural member i e around an axis parallel to one of the folds 22 24 and 26 when the structural member of the present invention is twisted in this manner the semi ellipsoidal indentations slide against one another while maintaining contact this contact helps prevent failure and crumpling of the structural member upon such twisting thereby adding to the range of rotation tolerable by the structural member the semi ellipsoidal indentations also lend structural rigidity to each individual sheet by interrupting the planar face of the sheet thus increased strength and rigidity is experienced with respect to forces applied perpendicular or parallel to the long axis of the structural member while rotational and torsional flexibility is increased the structural member may be manufactured in any of several different ways die stamping continuous sheets of metal with semi ellipsoid indentations can be used to create flat sheets as shown in fig3 which can then be folded into the structural member along folds 22 24 and 26 alternatively sheets such as.