Abstract: A multi-stage frusto-conical trowel is towed by a machine which travels through a pipe and applies a layer of mortar to the inside surface of the pipe. The multi-stage trowel is carried on a rigid support member which is pivotally connected to the end of a towing rod extending to the rear of the mortar-dispensing machine. A first stage trowel with overlapping arcuate leaves is rigidly attached to the front of the support member and performs rough troweling of the mortar layer. A second stage trowel has overlapping arcuate leaves in which the leaf joints are offset circumferentially from the leaf joints of the first trowel. The second stage trowel is rigidly attached to the rear of the support member and performs finish smoothing of the mortar layer.