 So you don't know what flat border does, not a problem. Anytime you have a flat surface and you wanna apply some type of action to the border of that face, this is the target to use. So if we click on this face, the actions only get applied to the border. Same with this face, and this face, and this face. It's a little easier to see what it's trying to do if you set your action to mask, but basically, yeah, that's what it does. Hope that helps and as always, I hope you have a fantastic day and I'll see you around.