The Beiter Tri-Liner is used to mark the exact position of vanes (like e.g. Spin Wings, Kurly Vanes, Rite Flite Vanes, ...) on arrow shafts up to 7,2mm (9/32") Nock-out-diameter. With the Beiter Tri-Liner it is easily possible to adjust the position of fletching in relation to the string, as well as the distance to the end of the shaft.The positioning ring allows many different adjustements and an exact orientation of nock and fletching. The included red Tabs are for the exact positioning of the fletching in length and distance to the nock. Additionally they help to draw the line in the correct length. The Tri-Liner can be used for different lengths of feathers, for both RH or LH, Recurve or Compound.