Firstly stakes were driven into the ground to roughly mark out the positions for the cast iron columns; these points were then set precisely by theodolite measurements. Then the concrete foundations were poured, and the base plates for the columns were set into them. Once the foundations were in place, the erection of the modules proceeded rapidly. Connector brackets were attached to the top of each column before erection, and these were then hoisted into position. The project took place before the development of powered cranes; the raising of the columns was done manually using shear legs (or shears), a simple crane mechanism. These consisted of two strong poles, which were set several meters apart at the base and then lashed together at the top to form a triangle; this was stabilized and kept vertical by guy ropes fixed to the apex, stretched taut and tied to stakes driven into the ground some distance away. Using pulleys and ropes hung from the apex of the shear, the navvies hoisted the columns, girders and other parts into place.