i have 3 bitzenberger fletch jigs one lines up perfect for 3 and 4 fletch the others are off some in other words with one jig on 3 fletch the nock feather is exactly horizontal to the string with the other 2 jigs it is off by 1/16th or 3/32 of being exactly horizontal to string and that puts one feather riding across the center of the shelf instead of the corner of the shelf the nock holders on my jigs are not marked either left or right and the 2 jigs with the problems are older one has brass screws and a lever to set off-set the other ones that works correctly and the one that doesnt have the round off-set knobs with the allen screws any ideas on this