The player can obtain HM06 Rock Smash on Route 36 on Pokémon SoulSilver version. The HM06 Rock Smash is very useful in Pokémon HeartGold and SoulSilver outside of battles in getting around and in obtaining Pokémon species and items that are hidden in rocks.
On Route 36, the player will encounter a girl, who was previously met, looking at a suspicious looking tree that will turn out to be the Pokémon Sudowoodo. The Pokémon will be blocking the path to National Park, Ecruteak City and Violet City. Using the Squirtbottle, the player can talk to the tree in order to engage Sudowoodo to a battle. After defeating Sudowoodo, the player will receive Berry Pots, Oran Berry and Pecha Berry as a reward from the girl. Once the girl leaves, the player can obtain HM06 Rock Smash by talking to a man nearby.