you'll need the pencil torches they recommend.
ACE hardware has them and they are not cheap.
but you just aim the pencil point to cross at the neck.
I keep a handful of junk cases by the machine for set up.
you can eyeball things, but the actual cases will show you exactly where you need to be.
then you lock everything down.
be prepared with a metal pail or pan or something to catch the cases as they fall out and another one to replace it with.
I'm using a little galvanized pail I cut the edge off of to catch them coming out.