During the welding‑cell setup of a chassis line, the roller‑actuated limit switch is mounted on the guide rail that moves the workpiece holder. As the holder slides forward, the roller follows the edge of the moving carriage and trips the switch the moment the holder reaches its predefined stop. The signal instantly cuts power to the drive motor, preventing overshoot and protecting the positioning pins. In body‑shop robots that position doors or windows, the same type of switch is fitted to the robot wrist; the roller contacts the gear housing and signals the controller when the tool has reached the exact insertion depth, allowing the PLC to start the next clamping sequence without manual measurement. The compact actuator also serves as a safety interlock on paint‑booth doors; when the door is fully closed the roller depresses the switch, confirming the enclosure is sealed before the spray system is enabled. A similar installation can be found in material‑handling conveyors that feed stamped parts to the assembly line, where the roller switch detects the arrival of a pallet and triggers the indexing motor.