Answer these questions to help you choose the proper construction level • Will the laser level be used indoors, outdoors, or both?     To use the laser visually for interior construction, choose a level tool with a highly visible beam, either ~635nm red laser or ~530nm green laser. You will need a laser level detector for outdoor work, as even a highly visible green laser will be lost in daylight. Laser construction levels designed for interior work will also feature variable rotation speed or beam scanning to maximize visibility. • Can the laser level be disturbed by laborers, live traffic, or heavy equipment?   If you work on large, busy sites, self leveling is an absolute must. A self leveling construction laser corrects for slight disturbances from wind or vibration, and will shut off for greater disturbances.  Manually leveled lasers must be periodically checked and re-leveled to assure accurate results. This is fine for small, well controlled sites such as house foundations, or deck and landscaping work. Self leveling lasers are a must for larger jobs and commercial buildings.    Self leveling is achieved by either a servo motor system or a compensator, both which can provide similar accuracy. If you are placing the laser level on a 12 foot tripod for machine control work, or up on wall angle for suspended ceiling installation, a servo leveled laser is handy because it does not have to be rough leveled. Compensator leveling systems have to be roughed-in before they can self level and are simpler electronically. • How much accuracy do you need in your construction laser level?   Rotary construction laser accuracy starts on the low end at about ±1/4in per 100ft (6mm per 30m) for inexpensive manually leveled products, and increases to as fine as ±7 arc sec (.040in per 100ft or 1mm per 30m) for self leveling lasers. Error increases with distance from the laser transmitter.  If a laser's accuracy is ±1/16" at 100ft, it is ± 1/8" at 200ft and ±1/4" at 400ft.  The best accuracy comes from working as close as possible to the laser level. • Do you need a laser level tool that can also project a slope?  . Construction lasers for precision slope (storm sewers or airport runways) have mechanical or digital counters that enable entry of slope in increments of .01% or better. For less precise applications such as drainage ditches, there are self-leveling lasers capable of manual "slope matching". • Do you need additional features, such as vertical alignment, or 90º layout?      If you need to perform layout and alignment tasks that go beyond the basic level tools, there are a variety of features available.  There are laser construction level tools capable of projecting a vertical plane of laser light for layout, or plumb alignment.  Laser level tools are great for taking base lines or layout points and transferring them to a ceiling, or upper floor.  There are models with a plumb laser spot that forms a 90º reference to the plane of laser light.  That 90º reference can be used for square layout, or to transfer single points up and dead vertical.  This is really handy on a windy high-rise job and for special needs like elevator shaft control points. Decision Guide Laser Reference, Inc.  •  USA Toll Free 1.800.238.0685  Click on the links below, or visit our lasers page for further information. Lasers primarily for precision leveling • commercial concrete and general construction Lasers primarily for precision slope and drainage • underground and grading Commercial interior applications • ceilings, walls and floors, layout and point transfer Residential applications • versatile, very low cost, interior and exterior capabilities Specialty applications • cone laser for drainage or collection, especially sports fields Laser level tools with vertical layout and alignment capability Laser level tools with a highly visible beam Laser level tools with a 90º plumb beam for point transfer and layout Laser level tools with slope matching capability, or rough slope