Gerudo Membership Card

From Zelda Wiki.org

This key item in Ocarina of Time allows Link to pass through Gerudo Fortress without being thrown in prison. Link obtains this from Nabooru's second-in-command after sneaking past all of the Gerudo Guards and freeing the 4 carpenters, Sabooru, Shiru, Jiro, and Ichiro. This is vital when journeying to the Spirit Temple for the first time, as Link needs the card to have the gate opened without being caught, as well as being able to walk around freely and being able to participate in the horse challenge and training grounds.