10 points to Paul .. it looks to me like one of the diffraction grating or piezo type line generators to me but same effect and same result.

The line is actually not a line at all but a series of dot being deflected in a pattern ... its the cheapest and easiest way to make this device and works the same as your surveyors device.

Not really hard to work out was it laugh

Last edited by Orac; 11/20/13 03:55 PM.
I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.