These fit over limbs and can show the straightness of limb alignment. Available for Recurve width and Compound Single piece limbs. A useful tool for tuning and set up, but beware of false readings when the limbs are not sitting straight in the riser.
Paperback by Larry Wise. Well known Pro compound shot in USA and good teacher of how to shoot well with a compound. Freshly updated. The info is good and teaches the principles of how to set up a compound for the most forgiving shooting.