There's no distinct line. They overlap a bit. The only way I've seen to make them separate is to slice through the fat line separating them and physically take them apart. It's not really that crucial to totally separate them (IMHO of course...).
Try searching for an Aaron Franklin video....
I'm not sure what's going on here, mub, but this is an old thread that popped up for some reason.
You separate the point from the flat only if you want to during slicing.
You mention a 19.5". I don't know about inches, but if you're talking about pounds you'd better get the fire going right now!