Was riding the 79 today and I came upon a group of riders coming in the opposite direction. I gave them the two fingers down low wave and most of them gave it back, but two of them tapped their helmets. Hmmm, never saw that before. I looked down and saw that my left turn indicator was on, so I figured the helmet tap meant to check my indicator. A little way down the road I spotted a cop hiding in the bushes on the side of the road. Hmmm, maybe that helmet tap meant "look out, speed trap ahead". Well, when I got home I Googled rider signals and sure enough, the helmet tap means cop ahead. Don't know who those riders where, but I wanna thank them for the heads up!