Hi Janice and Janelle,
Faux leather backing and Pellon absorbs rubber cement. In addition rubber cement evaporates, here is the funny thing, if the rubber cement is fresh it soaks into anything porous because it is so thin or liquid. At that point you have to use a few coats of it so that it stands or builds up on top of the material. As you use the container of rubber glue it thickens because it is evaporating, but when it gets the perfect thickness it holds better on porous material, if it gets too thick then it’s rolls off or clumps up and becomes harder to use.
Janice I think you are talking about straps. The wider is the outside material pattern so that the edges of the straps or handles are turned and finished, once sewn. Then the strap is folded in half and sewn. If I’m wrong about what part of the bag you are looking at let me know.