If you are shooting a sector frame on a self supporter, make sure you follow the leg all the way down the tower. Say you took the straight section put it on the ground in the middle of the tower. Look up inside the tower imagine where the leg would be that the frame is attached to all the way down. Shooting off the bottom of the leg will throw you off up to five degrees. Make a reference point and take your time. Teach some of the smarter guys on the crew how to use a compass. Triple check it and it will save you time in the long run. I have never had any issues.