Yep, both arms fully outstretched. Big roundabout, they had to take the third right, and he stood by the 2nd right. Really badly signed away, the organisers said that everyone on the course should know the route which I thought was a bit harsh. Only realised what the marshall was really doing when two cyclists stopped on roundabout and asked where to go! Sure they thought I was shite also, but did enjoy helping out!
I was marshalling at a Wakefield triathlon a couple of years ago, at a roundabout. Sat down for a coffee break, but then the guy who took over from me (member of the local triathlon club!) started throwing both arms up when the cyclists arrived, instead of directing with his left arm, causing one chap to cycle off in completely the wrong direction. There was no way I could have run after him.
I took back over pretty quick, as there was carnage on the roundabout as others were stopping in confusion. About 10 minutes later this poor cyclist found his way back, and yes, I got his thoughts full on. I was mortified by the mistake, it would have ruined his day.
I had a DNF due to my own stupid fault of trying to run and ignore a stress fracture. There was no way to get off the course, so had to walk over 3 miles back to the start/finish, and the streets were lined with spectators giving me funny looks. Took my race number off and kept my head down, was mortified. 20 mile drive home afterwards wasn't pleasant either.