What safety device should be engaged when a load is elevated?

The safety device that should be engaged when a load is elevated is the anti-fall device. This device is crucial for preventing load slippage or falls from heights, which can lead to serious accidents and injuries. When a load is lifted, it is essential to ensure that it is securely held in place, and the anti-fall device serves this purpose by providing an additional layer of safety. It acts as a fail-safe to catch any load that may become unbalanced or improperly secured while elevated.

The other options, while they serve important roles in forklift safety, do not specifically address the risks associated with elevated loads in the same way. A fork lock is typically used to secure the forks to the load, a manual brake is used to prevent movement when the forklift is stationary, and warning lights signal danger to nearby personnel but do not directly secure the load itself. Thus, the anti-fall device stands out as the primary means of ensuring safety when handling elevated loads.