The metal strip experiments demonstrate that lordosis of a
vertical elastic structure can be increased, without loss of
vertical position, by pull at the upper part of the structure,
provided pull takes place in a specific direction within
narrow limits; pull in other directions annul vertical position. Increase of lordosis is attended by opposite motions
of the upper and lower parts of the strip (Figure 5a). Any
given degree of lordosis of the elastic strip can be stabilized by tightening the pulling string in the specific direction