Instructions
Go to Route 111 and speak to the man standing beside the tree. After exchanging a few words with your character, he will give you TM43, Secret Power. Navigate to the "Technical Machines" section of your Bag.
Teach TM43, a Normal-type move, to one of your Pokemon. Every Pokemon that is capable of learning Technical Machines in "Pokemon Ruby" can learn TM43. This move's base power is 70 and its accuracy is 100 percent.
Walk up to a small indent on a wall or cliff. You can find these indents in the following routes: Route 116, Route 123, Route 119, Route 120 and Route 113. Have the Pokemon use "Secret Power" to open up the indent.