Profile: Bolt Base Ltd. is a supplier of standard stainless steel and high tensile fasteners in a wide range of sizes & pack quantities. Cup square carriage bolts, also known as coach bolts or mushroom head bolts is manufactured from 304 stainless steel. Carriage bolts are often used in timber construction. The square underneath the head jams in a drilled hole in the timber eliminating the need for a spanner or other tool to grip when tightening a nut to the other end. Alternatively, the square can be inserted into a square or slotted hole in a metal plate. Round connector nuts are used for connecting two lengths of threaded rod or two long fasteners if required. Our nuts are manufactured from A2 stainless steel which offer corrosion resistance and are almost non magnetic.