Edger - Floor Prep Wood Sub Floors
Floor sanding edgers are tools used for refinishing wood floors, but can be a very effective tool for leveling (flatten) out minor humps on plywood or other types of wood subfloors. In cases where plywood subfloors may have been exposed to a lot of moisture or rained on heavily during the early stages of having a home built, plywood edges can sometimes raise, curl and swell. Failure to correct is likely to cause squeaking at a later date because the boards will have voids under them once installed.
Some may think, "why bother, we can just use a regular belt sander." Belt sanders do not compare to the power output of a 
flooring edger. Using an example, a common belt sander usually takes 3-4 times longer than this great addition to your possible floor prep tool list. It will also require more sanding belts to do the same job.
Words Of Caution
Words of caution when using an edger. Always set any nails or screws that may protrude from the subfloor. Setting can be easily accomplished not with a nail set, but a large regular screwdriver laid on edge on the subfloor and a few whacks with a hammer. The edger can knock nails down in quick fashion and throw off sparks, but you'll find yourself buying more and more sanding discs once they get caught on a nail the wrong way. Edgers are not a difficult tool to operate. All come with a dust vacuum attachment port but do not remove all the dust.
What Kind Of Sanding Grit? How Many Discs?
For this type of work the lowest available grit will work. Most home improvement stores go as low as 36 grit. For minor prep and plywood seams you probably will not need more than three or four discs based on 1,000 square feet. That is unless you miss setting a few nails. Discs will rip apart and become useless.
See The Wood Floor Prep Video
I also have a page that covers more wood floor prep that involves fixing low spots.
