Guide rails are precision-machined steel T-section tracks installed vertically inside the elevator shaft to guide the movement of the elevator car and counterweight. They maintain the horizontal position of the car and counterweight during travel, support the safety gear forces during an emergency stop, and provide the reference surface for guide shoes or rollers. Guide rail cross-sections are standardised (e.g., T82, T89, T114, T127) and selected based on the rated load, rated speed, and safety gear type.