How to make material double sided.

Problem when using a cloth or leave with fresnel. IE the cloth is curled and in the render I see the backface. If you don’t use layer weight or fresnel it is ok, but when using that, you will get weird reflections.

I’ve seen a solution in the past, but I cannot find it back; I have to flip the normals. That way I will see at the back face the same material as in the front face. I am surprised that there is not a simple setting in Cycles to make a material double sided.

Any idea how to do that?

Aww sorry I suddenly found it.
From Greg Zaal.