Bending and twisting tube figure comprises two schematic drawings of a short piece of tube. In both drawings the tube is shown as being horizontal and one end and the side are presented to the viewer. The outline of the hidden end is shown as a dashed line. The ends are represented by ellipses rather than circles which indicate that the tube is at an angle to the viewer. The first tube is subjected to bending. At one end there is an arrow pointing down and at the other end there is an arrow pointing up. The second tube is subject to twisting. The arrows in this drawing are curved into semi-circles and represent a direction of rotation. At one end there is an arrow pointing in an anticlockwise direction and at the other end there is an arrow pointing in a clockwise direction.

 2.3 Prototyping and improving