threading is actually plucking the hairs with string.
get some thread 10 inches long, tie the two ends together. hold out your thumb and fore fingerand twist the loop around 10 times. so now you have your thumb and fore finger on each side with 10 twists in the middle...now open and close either hand... you got a zipper going on in the middle.
now bring that zipper to some hair... (sorry to gross you out people) do this to my belly button area... the hairs get stuck in the zipper and pluck them out. that's my ghetto way of threading. i only do this on areas i can reach. i cannot do it on my face. but that's the basic idea of threading.
in most salons the women instead of tying the ends together, put one end in their teeth. one loop with their thumb and forefinger, and the other end with their other hand. helps to aim and be more accurate.
does that make sense...?