Abstract: An alignment line supporting assembly is provided with releasable locking means for attachment to a rail of a railway track. Each assembly includes a pair of spaced reference line support devices having respective line support arms positioned outside the track to which are coupled respective ends of a tautly drawn string or wire. Two pairs of support assemblies are preferably provided on respective rails to establish reference lines on either side of the railway track. Measurements are made between a vehicle adapted to ride the rails and the reference line at various positions to ensure the correct alignment of the vehicle for railway operation.