I find my understanding of flags to be significantly lacking. Example: I thought the RC had shortened course and so I finished. Immediately, the racer behind me hailed "one more time around boys" or something to that effect. We undid our string, rounded the leeward mark in about 10th instead of first, now half a lap behind. Made it back up, but thats another story. Had I know what the flag meant I might have built a big enough lead to actually correct out.