This U shape tying jig is a portable,tiny but effective for tying your slingshot band. You can easily catch it in one hand to roll it over for better coordinating with another hand. It is made from high density plastic and can last for years.
There are 4 holes at one side, which is used to adjust the position of the screw pin. This U shape tying jig will only work for the pouch with center positioning hole. You also need a forceps to clamp the bands.The forceps is also available as one option in this link.
Have a look at one of the picture, you will know how easy it is to use this U shape tying jig.