the point of contra flexure is a point where
Contraflexure In a bending beam, a point is known as a point of contraflexure if it is a location at which no bending occurs. It is also known as an inflection point. In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero line. In other words where the bending moment changes its sign from negative to positive or vice versa. Knowing the place of the contraflexure is especially useful when designing reinforced concrete or structural steel beams and also for designing bridges.
Restriction map If you know of a restriction site placed towards one end of the insert you can determine the orientation by observing the size of the fragments in the gel. Often the orientation of inserts is important and this technique is used to screen for the correct orientation.