Lighten up end grain
When staining wood, making end grain match the faces of a board can be tricky, especially in porous woods such as oak. The open ends of the grain soak up more stain pigment than the less-porous faces and edges. Sanding closes up some of those open cells, slowing the intake of the stain. The finer the grit, the less pigment will stick. For end grain on porous woods, a good rule of thumb is to double the grit. So, if you sand through 220 grit for the faces and edges, continue sanding the end grain up to about 400.
—from the WOOD® shop