Unless, like Rob suggests, the knife is totally on the back of your arm with a full wrap-around guard, the blade tip should point up your arm, so if the string hits the sheath it slides along, rather than getting caught under the handle. I made one using a flat-handled CRKT with a half-wrap guard and the knife on inside, and it causes no problems. But you know, like neck knives, they look cool but there's really no practical gain over wearing the knife traditionally on your belt. Check out the armguard on the cover photo of T.J. Conrad's "Traditional Bowhunters Handbook." Talk about swank!