Has this ever happened to you? You're getting the floor ready for stain and the inevitable happens: burnished edges. The next thing you know, the floor is picture-framing when it's stained. This is a common problem many floor sanders face when they don't understand the principle of scratch patterns. In many cases, floor sanders will do their final drum sanding on the floor with 100 and their final edge with 100 grit. However, many sanders will use a backup pad under the edger, causing a softer cut. The result? This cut will be equivalent to one grit finer (such as 120) and will polish the edges and close down the grain.
To avoid inspections, floor sanders should either go up one grit for the edger when using a backup pad or drop down one grit on the drum. Secondly, stretching out the paper on the edger will close down the grain. When you are ready to turn the corner on the butt wall, change the paper regardless. Sharp paper usually won't close down the grain and polish the floor like the one in this photo.