According to standards, when shooting a trench with jacks, where should the jacks be installed?

The correct choice is to install the jacks from the top of the trench to the bottom. This approach is essential for ensuring the stability and safety of the trench during excavation work. When jacks are positioned from the top down, they can effectively support the walls of the trench and prevent collapses, which are common risks when working in deep excavations.

By starting at the top, the jacks can distribute the weight and manage the pressure exerted on the trench walls more effectively. This method allows for better monitoring and adjustment of the supports as the excavation progresses downward. It is crucial for maintaining safety standards in excavation practices, particularly in conditions that may compromise the integrity of the trench walls.

In contrast, installing jacks from the bottom to the top, from the sides inwards, or at random points would not provide the necessary support and could lead to significant safety hazards. These methods do not align with the preservation of structural integrity needed during trench work.