In the Dune universe of Frank Herbert, a sandrider is a Fremen male who has mastered the technique of riding the sandworm of Arrakis. This event is an important rite of passage in Fremen society, conferring adult status.
To become a sandrider, the candidate must successfully call and capture a sandworm, using the long Maker hooks to open one of the worm's front segments, simultaneously anchoring himself on the worm's back and forcing it to stay above the sand. Subsequently, the other members of the troop who gathered to witness the rite climb onto the worm's back behind him.