How to get a plane to intersect and join/merge with the perpendicular plane? I'm trying to model my house as a way of learning Blender. I'm having a problem filling in a small hole after following a tutorial about roofs.
It's best demonstrated with a video, but basically I want the extruded edge to 'collide' with the perpendicular edge but no matter what I do, it doesn't seem to snap to the edge it collides with. I'm always left with two unrelated planes which also means I can't make the small trianglar area at the top into it's own face.
Hopefully this question makes sense once you've seen me extruding the roof edge towards the house:
https://www.youtube.com/watch?v=ZDGNVaY2G-8&amp;feature=youtu.be
Sorry for the youtube link but it seems this StackExchange site doesn't like large GIFs, APNGs or anything else I've tried.
You want to stick this edge to this face but this is not a clean topology because your edge will just float, you should first use the knife tool to cut the roof and the left side, in order to add vertices, then fill with faces between the vertices with some F, and at last delete the inner faces:

Edit with your current file, as we can see you have floating edges, inner faces, etc:

What should happen: