You will need to know how to tie a good knot for this step.
1: slide the surgical tubing onto one of the wheels
2: slide it ont othe other wheel
3: make sure there is abuot the same amount of tubing on both sides of the gun
4: tie a good knot to the white rod at the back of the gun
5: tie a good knot to the white rod on the other side
6: make sure it is firm, but not tight