Final answer:
When coupling a semi-trailer, the front trailer supports should be cranked just enough to lift the front of the trailer off the ground. This ensures stability and prevents potential damage to the trailer and towing vehicle.
Step-by-step explanation:
When coupling a semi-trailer, the front trailer supports should be cranked just enough to lift the front of the trailer off the ground. Cranking the supports too high or not cranking them at all can lead to instability and potential damage to both the trailer and the towing vehicle.
By lifting the front of the trailer off the ground, it allows the weight to be distributed more evenly between the trailer's wheels and the towing vehicle, ensuring a stable and safe coupling.