As a disk sander is moved over the floor, the grits make spiral scratches that necessarily cross the grain of the wood. A drum sander, however, can not reach the last few inches of floor nearest the baseboard. Electric edgers, which are small disk sanders, are available for sanding these edges of the floor or they may be done by hand. Sandpaper Sandpaper acts by gouging fine slivers from the wood surface, leaving scratches, the size of which is governed by the size of the grits on the paper. Coarse grits act rapidly, but the scratches they leave are conspicuous, especially if they cross the grain of the wood.
Fine grits act slowly, but the scratches left are too small to see.
Scratches are least noticeable when they run with the grain of a wood. Scratches must be especially fine to escape detection on a wood with close texture, such as maple, and must be still finer to remain unnoticed if they cross the grain of the wood. In sanding a floor, time is saved by starting with coarse sandpaper to remove the grosser roughness and imperfections and to make the floor level as quickly as possible. The scratches left by the coarse grits are then removed by successive sandings with a finer sandpaper. The scratches left by the last paper should be too small to be observed even after the finish has been applied.