Most modern sailboat races are run on windward-leeward courses designed to give racers the maximum number of chances to pass each other and to create lanes. While theres little doubt that these new courses (until the mid-1990s, most racecourses were triangular and featured more reaching) make for exciting racing, they do create a problem for drivers and trimmers, namely that it can be tiring to crane your neck back in order to see the Windex on the top of the mast, as its harder to feel the breeze when sailing dead downwind. Also, when sailing by the Windex, its easy to miss any windsheer between water level and masthead height.
Luckily, theres an easy solution that requires only two pieces of string and some sail tape. Simply cut two telltale lengths of yarn and tape these to your boom (if you have end-boom sheeting, try affixing the tape between the boomvang and the end-boom fitting; if you have mid-boom sheeting, try affixing the tape abaft the mainsheet gear). Not only will this save your aching neck muscles, it will also give your trimmers and helmsman better insight as to any windsheer or localized shifts that might be influencing the racecourse.