You might not really need these, but they sure come in handy if you have them. These little gizmos use a set of camming rods to grab a stud to install or remove it, without destroying the threads. They work much faster than “double-nutting” and provide much more torque. A 5/16” one is the most useful, though one for 3/8” comes in handy for head studs. You might add a 10mm for T-Types, also.