Problem with the most common design (1/4+3/8 step screw with square cap, which goes into the hot-shoe, three knurled jam nuts, one knurled coupling nut) is that you can't apply enough torque by your fingers, while these nuts don't have any flats to grab on with a wrench. Using pliers is a bad idea because it kills the knurled surface.
So, here is my own version of this attachment, described in details.
Here, it's used to attach the arm to a piece of T-slotted aluminum profile.
1/4-20 threaded stud, made together with joint ball (blue) is screwed into the coupling nut (green). To make this link rigid, jam nut (orange) is used.
Step screw itself is not visible. It goes inside the T-slot and it's fastened there by 3/8-16 flat flange nut (yellow). Fiber washer (red) adds some friction there and helps to avoid scratching the surface of profile.
Coupling nut (green) is screwed onto the 1/4-20 portion of the step screw. In case, if 3/8-16 portion of it is longer than in my case and sticks out from the flange nut, metal washer should be placed between the flange nut (yellow) and coupling nut (green), because coupling nut should not be jammed against the shoulder of the step screw.
Every fastener here can be tightened by wrench.
If your articulated arm is equipped with joint balls (blue), having two flats on its flange (wider portion between the ball and the stud), don't use it to tighten it and jam the coupling nut against the flange itself - in certain cases it can bring certain problems.
If you are not going to use this arm in any other setup, you can permanently attach the coupling nut to the stud by using some Loctite thread locking liquid.
Replacing original nuts also helps to reduce the weight, if it's important.