Final answer:
In lifting operations using a jack, the blocking is placed under the load to provide stable support and ensure safety in case of jack failure.
Step-by-step explanation:
When using a jack, the blocking should go under the load. Blocking is a critical safety measure used to support the weight of the load after it has been lifted by a jack. This prevents the load from accidentally falling if the jack were to fail, by providing a stable and immovable base. Placing blocking beside, on top of, or in front of the load would not provide the necessary support and is therefore incorrect. The correct positioning of blocking is vital to ensure safety during lifting operations.