Torches are probably some of the most versatile items in all of Minecraft. They do the obvious things like lighting up dark areas and keeping monsters away. However, they have some other useful abilities.
As you may know, Sand and Gravel blocks are affected by gravity. So, if you remove the block underneath, they will fall. At that moment before the block falls, you can place a torch. This will cause all of the blocks to be broken allowing you to collect them. As a fun bonus tip, you could also place a torch beneath you when digging upwards to prevent Gravel or Sand from falling and killing you!