How to measure your horse for a rug-

L ;     Start at middle of chest following around point of shoulder to the end of rump but
 not wrapping around at rump.

Sh :  Start at bottom of neck where the wither begins, follow down the shoulder and around to
 the middle of the chest  where the rug should sit comfortably,not too low to sag around the
 shoulders and not too high to cut into his neck.