When the load calls for more than a 3/16-inch bolt can handle — handrails, grab bars, shelving systems, bathroom partitions — you move to 1/4-20. The 1/4-20 thread is a standard diameter in hardware, meaning matched nuts, washers, and accessories are easy to find, and the toggle mechanism inside the wall spreads the load across a wide surface area rather than concentrating it at a single point. 3-inch length handles most standard and slightly deep hollow wall assemblies. 1/4-20 thread is the right choice for medium-duty handrail and grab bar installations in residential and light commercial work — strong enough for a occupied bathtub rail, not over孔ed for a bathroom mirror mounting. Zinc-plated for indoor use. Round head flush installation. 50 pieces in a box. Standard on plumbing and bath Stocked at Crofton Lumber and Akron Lumber.