Abstract: A device includes at least one telescopic crane jib having a boom and a boom extension. A working implement is fixed to the telescopic crane jib by a rotary joint arranged at the boom extension and which has two mutually spaced rotary bearings. Hydraulic lines lead from the boom between the spaced rotary bearings of the rotary joint to the working implement. In the region of that end of the boom extension, at which the rotary joint is arranged, is a guide or the hydraulic lines, which guides the hydraulic lines from the boom extension to the region between the spaced rotary bearings of the rotary joint.