English to Chinese Bus/Financial Construction / Civil Engineering

In all cases where work may be permitted off a portable ladder a risk assessment clearly defining the controls where three points of contract can be achieved whilst performing the works, there is a ladder handler at the base of the ladder and the area clearly demarcated and free of hazards, such as horizontal starter bars.
有关安全使用梯子的，如三点接触的攀爬方法。

请教这句该如何理解，
这里的permiited off 什么意思，a ldder handler 是扶着梯子的人吗