Inversions of Kinematic Chain:

If in a four bar kinematic chain all of links are free, motion shall be unconstrained. While one link or a kinematic chain is fixed, this works as a mechanism. From a four link kinematic chain, four different mechanisms may be obtained by fixing each of the four links turn by turn. All of these mechanisms are known inversions of the parent kinematic chain. By this principle of inversions of a four link chain, various useful mechanisms may be obtained.