If the steel skelp bypasses the leveling process, it retains a defect called "camber" (a sweeping curve along its length) and "crossbow" (a bow across its width). If you try to feed cambered steel into a tube roll-forming mill, the weld seam will constantly twist and wander off the top-dead-center position. Tension leveling—which physically stretches the strip slightly past its yield point while weaving it through offset rollers—guarantees a perfectly straight weld seam line.