Fork cages are contraptions used by cranes to carry goods that are on pallets, from one area to another.
In essence, they’re like forklifts or pallet trucks that fly.
The forks are stored in slots in the base of the cage. The slinger will open the cage door and take the forks out with the crane once lifted slightly off the ground. Then they will slide the forks under the pallet of tools or materials. The crane will then lift it into the cage. The forks then go back into the base. The door gets closed and locked. Then the whole cage gets taken to its destination, where the load gets taken out using the reverse process.
This is a much safer method than the old design of just the forks lifting the load with a net over the top. There were instances of the net failing and loads falling off the pallet.