I use a phone app. Level Mate Pro. You can google it. I used all sorts of levels and they all worked but it was time consuming and I am a bit particular. Put in the Level Mate Pro and then leveled the trailer, and set the information into the app. Now, I can see just how much off level from side to side, down to the 1/2 inch. Place the levelers and drive up on them. Disconnect the trailer and use the app to level it from front to back. Actually works pretty slick. It is not perfect but it is an improvement from reading the bubbles.