Originally Posted by 1CharmShort

you can run two threads at once for decorative effect-for example when top stitching-

2 different colors (or the same color in both for a thicker thread look) ...use 2 thread spool posts or stands (on or off your machine-many machines have multiple spool posts available), thread each spool through your machine one at a time, and use the top eye for one, the lower eye for the other.
you can get some nice results doing this. you can also do it with a single eye, but you just don't get quite as even a distribution of color because one eye twists the threads a bit.
kinda fun...

found some videos of this on YT

https://www.youtube.com/watch?v=E_gK99yRwiM

https://www.youtube.com/watch?v=nS0qjcVh1R0

https://www.youtube.com/watch?v=PL5s5jTv1-0

https://www.youtube.com/results?sear...sewing+machine

oh... you could actually use a spool of thread and a bobbin together on 1 post if that's necessary