Whet stone (Fallout 3)

 is an item in Fallout 3. In real life it is used to sharpen knives and cutting tools, in the game it is useful only as Rock-It Launcher ammunition. It uses the same prop design as a paperweight.

For some players they can be useful for propping weapons on display in their houses

Locations
Whetstones are relatively rare. One can be found in an abandoned farm (random-encounter location) to the west of Vault 101. A rare Wood Chipper and a Mini Nuke can also be found in this location. There's also one in the Scrapyard by the house that needs a key. You may also find a few whetstones for sale from various scavengers. One can also be found on a shelf at the start of your escape from Vault 101. You also can find it in the Craterside supply Inventory, although it is very rare.

Furthermore they are known to be found in the South-East corner of the Deathclaw Sanctuary.