Mechanical devices designed to exert force in two opposing directions, propelling or drawing objects, form the core of numerous industrial and everyday applications. A simple lever, for instance, can be configured to either thrust an object away or draw it closer. More complex examples include hydraulic rams and conveyor belts.
These opposing force mechanisms are fundamental to automation, material handling, and various manufacturing processes. Their historical development, from basic hand-operated tools to sophisticated automated systems, has significantly improved efficiency and productivity across industries. This ability to precisely control linear motion is essential for tasks ranging from assembling delicate electronics to moving heavy loads.