The classical form of this character more closely resembles a gate:

Memory hook Resembles the outline of a door with hinge on the left.

Combinations

Chinese	literally	English
大门	big door	entrance door; front door
门口	door mouth	doorway

Dialog

Chinese	literally	English
门口大不大？	door mouth large not large	Is the doorway large (or not)?
门很大	door very big.	The door is very large.

[1] Temple gate door by user gunnsteinlye from http://www.flickr.com/photos/gunnsteinlye/3071667001/ under license: Attribution-Noncommercial-Share Alike 2.0 Generic