There are times when one needs to sand a surface that is not easily accessible by our pudgy digits, even if using something as ingenious as Tight Spot Sanders. I recently had need to do a little sanding in just such an area. Years ago, I had made (and misplaced) a functional little sanding tool. I decided to (re)make one. It's a simple thing. I used 0.125" styrene rod, sawed at an angle using a razor saw, a piece of 0.040" x 0.100" strip (0.040" x 0.125" would be more logical, but I am out of that size,) two-part epoxy, and sandpaper. Glue the strip to the angled face of the rod, let dry, then attach sandpaper to the bottom of the strip using two-part epoxy, let dry again, trim the edges of the sandpaper, and you're ready to use. You could make several using different grades/grits of sandpaper.