The M 4000 multiple light beam safety device from SICK is used for access protection to assembly lines and machines. It has a housing length of between 30 and 180 cm. The distance between the safety light beams can be individually defined. The integrated laser alignment aid for aligning the sender and receiver units is new. The extremely flexible mounting of the M 4000 is provided by three slots in the housing or through rotation around the end caps (swivel mounting). For the first time, configuration buttons and indicators allow more rapid and straightforward commissioning and diagnosis without the need for additional tools. A modern gluing process is used to integrate the front screen for tight and precise lateral protrusion in the profile. Its very slender appearance, preciseness of expression, and communication of flexible, universal applicability were major considerations during design.