Sanding blocks are as numerous as, well, grains of sand.
But the SandDevil block, invented by Connecticut wood sculptor Marv Beloff, stands out for its efficiency and ease of use. The best thing about the block is that it uses the 3x21-inch sanding belts that are made for power belt sanders. Since the belts are tougher, you get several times the longevity of blocks that use standard sheet sandpaper. You can rotate the belt around the block as it wears. Also, the belts snap in place with little effort.