Assign alternate (individual small backup) to a catalog?

I can't find the documentation on how to assign the individual small backup template to a catalog display...    I have 2 catalogs. One for sale and one for historial purposes.  The historic one has prices but no inventory.  We don't want an add to cart button on it, so I was told we can use the backup template for it, but I can't find out where or how to apply it...

TIA,

Jeff