Secure lock helps prevent blade from creeping during use16" and 19.2" stud center markings simplify framing jobsSpecial Tru-Zero hook does double-duty as a pivot for drawing circles and arcs.Three-rivet, corrosion-resistant hook for accurate inside/outside measurements.Mylar coated blade for extra durability1" wide steel blade remains rigid up to 7' for easy one person useHeat-treated spring for repeated useBelt clip on back of case for easy accessibility