Materials:
Nylon webbing - 1" x 38"
grommet
non-stretchy cord - 2 ft.
Fold the webbing in half, line up the two ends and put the grommet through BOTH ends. Sew the webbing together 1 1/2" from the other end.
Put the grommet end through the other end. Fold the cord in half and put the loop through the grommet. Tie a knot in the cord so the loop is about the distance to your finger tips.
To use, the cord should reach about to your finger tips so when you draw your bow there is a little bit of slack - about an inch or so. When you release, if your back tension is proper, the string will only travel that extra inch before your back holds it. If you are drawing with your arm muscles, you won't be able to hold the string back. The difference is night and day and should help develop back tension.