hello! I have made a castle that you can walk around in, but some wall are invisible.
How can i fix this, i have tryed ctrl+n but it didnt work. I have searced in the fourm but i didnt find anything. (If you want me to post a blend file you have to tell me how)
get the model in edit mode, select the face you want to flip, Press W and select Flip normals from the menu.
you can assign polys double sided as well…
Press F in object mode to enter UV edit mode, rightclick on the polys you want, and in the edit menu press the two sided button.
hope that helps
Yes please post the .blend. Just not that ctrl+N doesn’t “fix” your normals, it flips them to the outside (the convex side) of your object. To view your normals, click on the “Draw Normals” button in the edit buttons, under the “Mesh Tools 1” tab. Then you will have to manually flip your normals to their correct orientation. It is always a good idea to model your meshes with “Draw Normals” on so that you can flip your normals when need be, rather than after you’ve finished a project and have to go back through and flip them all again.
edit: Poof beat me…
Thx for the help it is working now 
Sure thing!