How do you get the power ring in Zelda the Minish Cap?

The Grip Ring is located on Mt. Crenel. Knock out a Buissness Scrub in a cave on Mt. Crenel and he will sell you the Grip Ring for 40 rupees. The Grip Ring is needed for Link to be able to climb up Crenel Wall. It can also be used on the far right of Mt. Crenel to climb up and down the shortcut. Link also uses it on Veil Falls.