Just go buy some rookies from ur local outdoors shop!
i was marshalling at a site and we were watching a guy crawing up the edge of the feild, out side the boundary. i was bout to pull him out and my mate (the other marshalle) pulled out a rookie, lit it, and rolled it next to this guy.....
needless to say he Shat himself, jumped up, and then get shot out by bout 5 people......
he learnt to stay in the boundarys....