Hi,
I’m very new to Blender and I’m following this tutorial on modelling a basic house. When I render, the roof has a small mark on it. And when I’m in edit mode there’s a little triangle near the top right darker than the rest.
What is it and how do I remove it? Thanks for reading.
Not sure what tutorial you’re following but it’s not a very good one.
I can’t see clearly from the pic,post the .blend file.
Care linking to the tutorial,that model is using way too many edge loops.
Hi
http://www.filedropper.com/house - The .blend file.
The tutorial I’m using is http://www.youtube.com/watch?v=LLV7h-WLIx0
Welcome deniedaccess!
Could be a number of things there… a duplicate polygon or an unwelded vert. It’s best to let us check out your .blend file so we can identify it for you. When I first started modeling, I used to do all kinds of crazy things accidentally and not know how to fix it. It’s all part of learning cg. 
Ok… yeah, you have some faces on top of each other. Just select the faces and delete them (x button and select ‘face’). When you have a nice hole there, go to vertex mode (you can click the button or hit cntrl + tab and select vertices) and notice that you have 2 extra verts on that edge that you don’t need. Delete them with x and select vertices from the list. Now select the four verts surrounding the hole and hit “f” (think ‘f’ for face) and make a polygon face there and voila!
This stuff happens sometimes so don’t be too discouraged. Just be brave about deleting faces. You can always rebuild them with that “f” trick. 
Thanks for your help, Tommy.
