Abstract: An assembly crossbeam for placing on a tower top, in particular on a tower top of a tower of a wind turbine, and to a method for drawing in cables, in particular tendons, along a tower, in particular a tower of a wind turbine. The assembly crossbeam comprises a main support having a first and second end, and two auxiliary supports, each having a first and second end, wherein the two auxiliary supports are positioned on either side of the main support with each of their respective first ends at the centre of the main support, wherein on the main support there is a first trolley which can move along at least a first section of the main support, and wherein on said main support there is a second trolley which can move along at least a second section of the main support.