Bill: The mainsail telltales are placed at the batten end. Additionally, you can place one on each side of the mainsail at about the middle of the sail. You read those two the same way you as you read the ones on the jib. Some mates say the mast distrupts the air flow to thsoe two telltales and it does but not that much. On the jib - divide the luff in 3rd's. Once you find those spots just place one on each side about 12" back from the luff. Once you get them attached you have to learn how to read them. Telltales are absolutely the most important sail trim indicaters on a sailboat. Later this month, there will be telltale quiz presented by Gary W (the sailor who comes up with all the monthly topics). After that, I think I'll do a piece on the subject of how to read the telltales and what sail trim adjustments they are telling you to make.In the meantime, your most important mainsail telltale to watch is the top one (it indicates twist) and the most important Jib telltale is the middle one. The top jib telltale tells you something is wrong and the middle one give you the adjustment you need to make.