I beleive stapleing is purly for cel distribution
of 2 or more cels (many layers) or a background.
In the actual process there are metal "poles"
which go through the holes you see in your cels.
They keep all the layers alligned and the scenes
run smothly because of this. Once the cels are in
place, a GIANT camera takes a picture of it or if
it is a pan cel, it pans across the desired area.
I hope this helps you.