When I started (and I'm still new to it) I didn't know this but I'll pass it along. You will want to lap the hell out it for more than just ensuring that its flat. You're also smoothing out the stone. I didn't know this at the time but you're supposed to try to strip off about 1/8 of an inch of the 4k side until it feels smooth. The Norton 4k comes fairly gritty and it needs to be lapped to smooth out the surface. If you don't, you won't be able to polish the edge at all.