Our swivel jack has a giant “T” on the bottom thats welded to the acme threaded stem. This vastly increases the load capacity as compared to swivel jacks that use two tabs and a bolt. Thread is a square acme thread and is very precise. Nut can be spun and will spin for several revolutions due to accurate mating surfaces. Giant 9 inch cast iron nut. Lower plate has holes for screw/nail or however you prefer to secure. Galvanized.