Hex nuts are one of the most common nuts available and are used with anchors, bolts, screws, studs, threaded rods and on any other fastener that has machine screw threads. Hex is short for hexagon, which means they have six sides. Hex nuts are almost always used in conjunction with a mating bolt to fasten multiple parts together. The two partners are kept together by a combination of their threads’ friction (with slight elastic deformation), a slight stretching of the bolt, and compression of the parts to be held together.
To ensure full thread engagement with the hex nut, bolts/screws should be long enough to allow at least two full threads to extend beyond the nut face after tightening. Conversely, there should be two full threads exposed on the head side of the nut to make sure the nut can be properly tightened.