Logismarket, the Industrial Directory.

The mobile ladder comes equipped with two retractable wheels and a draft bar (patented systems) which make moving the entire structure very easy.
This system also works as a safety barrier, as it blocks access to the top of the tank when the base of the structure is not blocked.
For use, the ladder is pushed against the side of the tank, where the height level can be adjusted by the use of the brake winch's crank. The ladder position is blocked by a gravity-controlled parachute; the handrail guarantees complete security for the operator while working in the area atop the tank.