Zenith mirrors redirect the light path inside a telescope, so that an easier viewing position is possible. Relaxed observing with a lens telescope (refractor), Schmidt-Cassegrain or Maksutov telescope is only possible with a zenith mirror.
Zenith mirrors are simply inserted or screwed into the telescope’s focuser. At the other end, you can attach the socket of an eyepiece. The common plug dimensions of 1.25" and 2" are usually used.
The zenith mirror can be removed in order to connect a camera.