Here I am commenting on something that I don't exactly understand. The way the thread holder is oriented has to do with tension. Some machines are made to turn the spool to take the thread off the spool (upright). Others are made to spin the thread off the spool without turning the spool (sideways). It has to do with the way the machine was designed to work.
I know that's kind of vague, but that's how I understand it.
bkay