Pipe lasers are used to provide a solid line to align pipes during construction and ensure that they are being laid in a straight line. The lasers can be set up above the pipe to ensure that it is being laid even with the ground, or they can be set in the pipe to ensure that the pieces are aligned.
The usefulness of a pipe laser is hard to overestimate. In addition to being used to keep your piping aligned and sitting at a proper angle, a pipe laser has a multitude of layout-related uses at a construction site to measure the evenness and alignment of any surface, not just pipes.When needed the lasers can be fitted onto a tripod or setup on a trivet plate that goes in the manhole or mounted onto a spreader bar that will span the manhole.
Because of its small size, a pipe laser has the benefit of fitting into places that a person could not normally fit into. It could be lowered into a sewer, for instance, and measure the grades of pipes that a person could not measure manually without digging.