Direct
Dear Mikey,Consider the shape of your sails as a triangle. These dimensions are the base and altitiude dimensions. I and J, I believe are the jibsail on a sloop rig assuming a 100% jib; and, P and E are for the mainsail. Jay is giving you the address of where they explain it. The jib base dimension may be a perpendicular from the luff line or fore/mainstay instead of the base dimension. Good luck in your quest,Mike DiMarioMedia, PAs/v SerenityH376