J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Keel Fairing - Trailing Edge Location

I'm planning to fair my keel this off-season and would like to know how you determine the proper location/placement (fore/aft) of the keel. The keel specs say that the "corner of the transom to the trailing edge (of the keel) at hull is 3820mm-3840mm."
Where is/what is the corner of the transom? How do you determine it? Etc?? Any info would be appreciated. Thanks.

Steve Sullivan
Temptation, #311