A device for aligning rail ends for welding of the abutting rail ends comprises a pair of clamping members which extend across from the rail to be welded to the adjacent continuous portion of rail including a telescopic member which can be expanded to abut plates at the ends thereof with the web of the rail and clamping members which extend over and around the rail to clamp the other side of the web. A jacking screw acts to lock the telescopic member in the required gauge spacing and also to jack the clamping member upwardly to locate the rail end at the required elevation.