The term "rear door" refers to a means or opportunity that is not immediately obvious, but can be discovered through careful investigation. It suggests finding an alternative way to achieve something by exploring all possible options and angles.
There are also child - safety rear door locks for added protection. (spitzersheffield.com)
Large rear door openings open to almost 90 degrees for easy access to the third row. (en.wikipedia.org)
The black bonnet, unique side glass, lack of rear door handles and the seamless rear end distract the eye though and the detailing in the rear lights is just gorgeous. (evo.co.uk)