TackingMaster mentioned at Sailinguru.com

TackingMaster mentioned at Sailinguru.com

The TackingMaster, an easy-to-use, mechanical instrument (no batteries required) helps you determine the favored end of the starting line and keeps track of shifts upwind and indicates the favored gybe when it comes time to round the windward mark.

http://www.sailinguru.com/extra-fun/tackingmaster/