A bolt is a type of fastener with an external helical thread that mates with a complementary internal thread, often found in nuts. Bolts are commonly used to hold objects together or position objects. There are different types of bolts including carriage bolts, eye bolts, hex bolts, and lag bolts. A nut is a fastener with an internal threaded hole that works with a mating bolt to fasten multiple parts together. Nuts come in varieties such as castle nuts, acorn nuts, hex nuts, and wing nuts.