A Door: Deleting Faces Problem?

Hi, ( Please see image: http://www.sightsea.com/extras/door_frame.jpg )

Cutting a hole for a door into a cube ( shaped like a wall ) I’m finding that if I delete the faces there remains a gap. It leaves the inside of the door hole open, as if you can see inside the wall.

Can some one clue me in on what I’m doing wrong, or how to fix the problem after the hole is made in the wall?



yeah… select 4 verts and press ‘F’(Fill)…

Thank you!