I bought mine already made and the rope is bigger than 3/8 probably 1/2". I think it was around 20 bucks. It isn't regular rope and looks like something rock climbers would use. It is easy to move up and down the tree as I use my climber. If what you are talking about is the long line going from the stand to the ground for use in a lock on stand with climbing sticks or a ladder stand then I would use a high quality 3/8" rope and tether myself with a prussic knot linked to my HSS vest. Years ago all I used were the dual black strangle straps that came with the lock on stands. The various safety vests along with the lineman's belt accessory make placing stands much easier and safer.