Spirit levels with mirror

 

— capsule for vertical control, equipped with an additional viewing window with a special mirror. Such a window allows you to see the "vertical" capsule not only from the wide side of the instrument, but also from a narrow edge. Thanks to this, when working in cramped conditions (for example, if the controlled surface is located deep in a narrow vertical slot), you can turn the level "edge" and check the verticality through a window with a mirror.