Laser Measuring Devices depend on the reflection of an internally generated laser beam to measure the distance between two points. In a very few instances, the distant surface will "absorb" or "refract" rather than reflect the laser beam, resulting in inaccurate measurements. This is inherent in the way a Laser penetrates a few specific surfaces and is independent of any specific manufacturer of laser measuring tools.
While this is an uncommon occurrence, there are certain materials, in particular Cultured Marble, that have demonstrated this effect. Cultured Marble is commonly used in doorway thresholds and window sills, but is not normally used on the sides or top of an opening except in wet environments such as a shower entrance.
If the laser dot gives an impression of a glowing area when shone onto a surface, rather than projecting a small dot of light on the surface, this indicates the material may be absorbing the light. As you are at this point not measuring from the surface of the desired material, incorrect measurements may result.
If absorption is observed or suspected, Solatech recommends that a target be used at the measuring point. This can be as simple as a sticky note, business card or a piece of masking tape. This will provide the necessary reflective surface to provide measurements within the accuracy of the laser measuring tool.
The Leica DISTO™ series of Laser Measuring devices are etremely accurate, with a typical accuracy in measuring of +/- 1mm, or less than 1/16th inch. However, under certain conditions the measurements can vary. Understanding how and when these errors can arise will allow you to have a very high confidence in the measurements provided by your Leica DISTO™ Distancemeter. For specific details go to: http://www.leica-geosystems.com/en/4890.htm (Solatech is an authorized Leica DISTO™ distributor).