Abstract: A trolley wire is paid out under tension from a drum on a traveling railroad car and is guided by a guide roller device on a following car to be hung by temporary hangers on a previously installed messenger wire, the guide roller device having a cradle rotatably supporting several transverse horizontal rollers and vertical rollers which respectively form a horizontal guide surface and two opposed vertical guide surfaces of large radii of curvature to prevent permanent bend sets in the trolley wire. The cradle is rockably supported on transverse pivot pins so that it can swing and optimally adapt to changes in the wire direction, and the mechanism thus supporting the cradle is also movable in the up-and-down directions and the in the transverse left-and-right directions.