Set the boat up on the beach. Sails up, but not sheeted in.
Take the main halyard and stretch it so that it's taut from the hook at the top of the mast to the top of one of the bridle bolts. (Usually on the windward side so that the sails don't interefere.)
Mark the spot on the halyard with your thumb where it touches the bridle bolt. Holding that spot with one hand, go to the back of the boat and stretch the halyard taut against the transom of the same hull. With your other hand, mark the spot where the halyard crosses the bottom corner of the transom.
The distance between your marked spots is your mast rake - could be anywhere from 10" to 20" depending on your set-up.
Each black tick on the Comptip halyard is approx. 1", so you can just count the ticks to get the measurement.
