If you've decided to invest in laser leveling equipment, you're already familiar with the benefits. To make the best buying decision, however, you need to understand the differences among construction laser systems. TYPES OF LASERS A fixed visible-beam laser is used as a grade line for applications such as pipeline or tunnel building, and as a plumb line for plumbing columns, walls, and similar vertical members. Rotating visible-beam lasers are commonly used indoors for tasks such as installing suspended ceilings, HVAC and electrical ductwork, and cabinets. Invisible-beam lasers are created by an infrared energy source located in the transmitter. Invisible-beam lasers are more commonly used for construction leveling because the infrared beams work better over long distances and in bright sunlight. LEVELING OPTIONS FOR INVISIBLE-BEAM LASERS For some laser levels, you manually level the laser plane by using leveling screws and bubble tubes. Accuracy of these systems depends mainly on the sensitivity of the bubble tubes used. Compensated systems are the most common systems in use today. Their transmitters are rough-adjusted by centering a bull's-eye bubble with leveling screws before a compensator does the rest of the leveling. A few systems use electronic self-leveling; there are no leveling screws on the transmitter, and the self-leveling range is much wider than that of compensated systems. RECEIVERS Electronic receivers (also called sensors) attach to a grade rod and indicate the laser beam position, usually with a visual or audible signal or both.