Hence, there is no need for complex actuators and that makes the method particularly cheap. One needs essentially a video camera (a high resolution webcam is well suited), a commercial hand-held laser line and the DSL software. Though it is not the purpose of this paper to describe how the system is operated (which is completely done by the software itself), it is important anyway to insist on some points to make it possible for beginners or non-specialists to evaluate whether they feel capable of managing the whole thing.