Changuards (and cases) can be attached with specially brazed on hangers or you can use clamps that clamp around various frame tubes to support them.

There are designs that circulate the chain through an oil bath. I believe old Raleighs did this, providing you with an oil port on the top of the case. It's not really that useful though, because once you fully enclose the chain, it stays pretty clean all on it's own. Hit it up with a good dose of heavy, sticky wet lube when you assemble the thing and you won't have to touch it for years and years.