Product description Quick action lock washer for fast height positioning. Patented Fall Guard feature allows 1quot; safety zone around lock washer. Set screw can lock jack head to stand for transportation - no loose pieces. Jack independently load tested for quality assurance From the Manufacturer Sumner ST-881 781300 Hi Fold-A-Jacks with "V" Head. Sumner's Fold-A-Jack jack stand has a sturdy 1-Inch square tube base construction, quick-action lock washer for fast height adjustment and 1-1/2-Inch Acme fine adjustment thread as the Heavy Duty line, but folds up for easy storage and transport. Includes one ST-881 781300 Hi Fold-A-Jack with V-Head.