Below is a list of Bolts manufacturers from Middleburg, Pennsylvania. A bolt is a type of threaded fastener that utilizes a nut to secure itself to a desired surface. Many bolt manufacturers produce industrial bolts that are used for high-stress uses, such as construction, or as components in the creation of larger industrial parts, machines and vehicles. Most bolts are made out of stainless steel, but some are made with other materials, such as titanium and aluminum which are also heavy-duty.