The mirror mechanism in a camera has very little pressure holding it in the down position to allow for a quick response when activating the shutter. As such when transporting the camera you should make sure that the mirror is lock in transport position.
This you do by simply detaching the digital back or film magazine from the camera body and attach the cover plate for the film plane that comes with the body.
Lens can stay attached, if removed then attach cover here as well.
If lens is removed you can very easily see if mirror is up or down.
Back is attached and mirror is down, the camera should not be transported like this.
Mirror is up and you can see background through the body.
Attach covers to front and back and the camera is now ready for transport.