Understand J-Channel at Roof Intersections

hey y'all so we're getting ready to patch in the siding on this project cuz we're getting close to the finish so I thought I'd be nice and share some siding knowledge with you learn you something and I'm sure you probably already knew this and you've been doing this forever but somebody might not so here we go so we're going to start patching in the siding and typical fashion you would start with a starter strip but in this case since we have a roof structure we have to start with J channel so once the J channel is installed water can just sit in there it could overflow so I personally don't like that so I like to go a little step further and I'll drill some we