We recently remodeled our kitchen which required refinishing the hardwood kitchen floor. The entire main level of our home is hardwood. There are three sections where there would be an "edge" where one side of the floor was refinished and the other side was not. The problem we are having is there is a noticeable dip and waviness in the section where the floor was refinished. We received estimates from multiple contractors and no one mentioned this potential problem and I honestly did not think to ask. I believe the problem was the contractor had to basically free hand the sander - there was no edge to butt the sander up against and I can understand how hard it must have been to try to control the orbital sander from going past the "edge" line and control how much material was being taken off. My question is do some contractors have a type of clampable guard that can be put down on the "edge" line to prevent the sander from going past the line. This would free the contractor up to only worry about how much material is being taken off.

A regular masking tape two layers thick, not pressed down too hard would be a good edge to work toward. I always go one full board more with the final coat of finish.