Packing iron strap is a popular‑colloquial name for steel strapping. In reality, packing‑iron strap is a slightly elastic steel band. Its actual material is steel rather than iron. In other words, common "packing iron strap" is just the customary designation for blued steel strapping. is a popular‑colloquial name for steel strapping. In reality, packing‑iron strap is a slightly elastic steel band. Its actual material is steel rather than iron. In other words, common "packing iron strap" is just the customary designation for blued steel strapping.