Pokemon Diamond what do you use to smash rocks?

In Pokémon Diamond, you need a Rock Smash HM to break rocks.

Here's how it works:

1. Get the HM: You'll receive the Rock Smash HM from the Eterna City Gym Leader, Gardenia. She gives it to you after you defeat her.

2. Teach it to a Pokémon: You need to go to a Pokémon Center and teach Rock Smash to one of your Pokémon.

3. Use it: Now you can use Rock Smash on rocks you encounter in the game. This will break them, opening up new paths and revealing hidden items.

Let me know if you have any other questions!