The holes on my lathe are on the left side of the carriage, for the follower rest.
I also use the threaded holes for the carriage stop, when I thread. Its a bracket that bolts to the carriage side that has a adjusting screw and a lock nut, that sets the carriage depth, when I thread. At the end of the thread cut, back out the carriage, reverse the lathe, when clear, stop, turn the carriage up to the stop, advance the compound, go forward and repeat, until the thread is done.