The Chain IK constraint lets you use Inverse Kinematics to constrain the movement of a chain. 
To constrain a chain of bones with the Chain IK constraint:
- Select a Chain IK constraint from the Asset browser’s Constraints folder and drag it into the Viewer window. - If you drag it into an empty area of the Viewer window, the Chain IK settings appear in the Constraint settings. 
- If you drag the constraint on top of an object, a context menu appears asking if you want to assign the object as one of the constraint’s operators. 
  Constraint context menu 
- Assign the objects that you want to be the first and last nodes in the IK chain to the First Joint and End Joint cells. 
- If you have a node that branches to more than one node, drag a node into the Effector cell to specify which one is the End Joint. 
- If you want, assign an object to be the aim of the chain to the Pole object cell. 
- Click Snap to activate the constraint without moving the constrained objects, or click Active to activate the constraint. Note: If you are using IkRPSolver, rotating the effector object does not alter the constrained object. See  Solver Type for more information.