An RSSR mechanism is analyzed by treating the linkage as two manipulators. The mobility region of the input link or the output link is found from the intersection region of the working volumes generated by both manipulators. By analyzing the intersection region on either the plane of the input link or the output link, the mobility region can then be calculated from the intersection of an ellipse and a unit circle. Concise discriminants and flowcharts are proposed to determine the type for several special RSSR linkages, such as spherical four-bar and simply skew four-bar. Grashof’s rule is also derived for planar four-bar linkages.