Abstract: In a well obstructor for a steel wheel lugs are shown for ensuring axial (and optionally radial) positioning of the obstructor relative to the wheel rim. Preferably such lugs are turned out of the material of a band-like obstructor across at least part of its axially intermediate portion. They may be punched and bent out of a metallic such band.It is also disclosed how such a band and its retainers may be adapted for automatic assembly on to the rim by being respectively placeable on the rim along respective radial straight lines.