interesting examples of linkages include the windshield wiper, the bicycle suspension, the leg mechanism in a walking machine and hydraulic actuators for heavy equipment. in these examples the components in the linkage move in parallel planes and are called "planar linkages". a linkage with at least one link that moves in three-dimensional space is called a "spatial linkage". the skeletons of robotic systems are examples of spatial linkages. the geometric design of these systems relies on modern computer aided design software.