T-head Bolt : A T-head bolt has a flat, T-shaped head which either fits into a slot or can be gripped with a wrench for tightening.
Stud Bolt : A stud bolt is a fully-threaded fastener used to hold two objects together. Stud bolts are used in conjunction with hex nuts on each end, while a stud is threaded, pressed or otherwise secured to an object on one end and a nut is used on the other.
Shoulder Bolt : Shoulder bolts have an unthreaded shank that is long in comparison to its threaded portion, which is located under the head. Shoulder bolts are used to locate one machine part to another, or as a plain bearing in places where rotary or sliding motion is required. Precision shoulder bolts are manufactured with varying diameter and shoulder-length tolerances. Shoulder bolts are also called shoulder screws or stripper bolts.
Carriage Bolt : Carriage bolts are round or flat headed bolts used to fasten metal to wood. Typically, the underside of the bolt head has a square cast-in pattern to hold the bolt in place while the nut is tightened.