A steel wheel is a 5‑high straight (A‑2‑3‑4‑5), the best possible low in many games.
Explanation. In lowball or Hi‑Lo games, A‑2‑3‑4‑5 unsuited is called a steel wheel—the best qualifying low or straight. The term reflects straight made of “steel” cards and wheel structure. Having the steel wheel often leads to strong showdown potential or scoop value.