Flex-I-Files are great tools for sanding curves like aircraft fuselages. But I’ve found that overenthusiastic or prolonged sanding can still produce an unwanted flat spot. To avoid this, I use sanding sponges available from hardware stores. They come in grits from coarse to very fine. I cut a thin strip from the sponge and super glue it to the non-sanding side of my Flex-I-File. This eliminates any chance of sanding something flat.

Tip submitted by:
Gautam RaoCommack, New York