There are occasions when a lathe dog is handy to drive spindle work when turning between centers on a wood lathe.
I needed to turn several hair pipes for an American Indian bead vest. The hair pipes are 3/8" in diameter with an 1/8" hole through the center and 4" long. The best method to assure the hole is actually in the center is to drill the hole first and turn the hair pipe using the center hole as reference.
Clamp the work in an appropriate chuck and through drill the work with a chuck in the tail stock. You will have to clear the drill chips at a drill depth of about every 4x the drill diameter. Turn the end of the work so it will fit in the lathe dog.
A Morse taper #2 dead center should be placed in the spindle and also a face plate attached as normal. The dead center will stick out a little beyond the face of the chuck. The lathe dog is clamped on the work piece which will be held between the dead center and the live center of the tail stock . The lathe dog is adjusted so the lathe dog leg just clears the face plate. A bolt is placed in the faceplate to catch the leg of the lathe dog to drive the work piece. Turn and sand the tail stock end of the piece and flip the work around to turn the other end. The outside diameter will be centered on the inside hole.
I bought my MT-2 dead center and small lathe dog from wttools.com. The lathe dogs are intended for metal lathe work and are made in several sizes for different diameter work. The dead center could be turned out of any hardwood. The lathe dog could also be made from hardwood and screws.