If you're hand-sanding the surface of any car that isn't a 1980s Volvo, you're going to run into issues with body contours. Malco's Conformable Sander, aimed at auto body repairpersons, is designed to solve that problem.
The flexible sanding block is first pressed against the desired contour, and an aluminum "memory bar" inside then holds that shape. Sandpaper is then attached to the inside and you're off to the races. And when you need to reset the block, you just press it back into a straight line with your hands.
Additionally, "A thin, ultra-flexible, paper-slide interface allows the block contour to be changed without buckling or tearing the paper," the company writes. "There is no need to re-position the paper, change the block contour, or remove the slide when changing out the paper grit or replacing worn paper."
The blocks come in 5- and 8-inch variants, and retail for about $50 and $60, respectively.