i had to do the pavement gantry with the truss out thrown off it! only 5 of the 9 people turned up! basically they just want to see your capable of working together and of thinking and communicating!
Just take your time and talk it through with the other lads and you'll be fine!
I did it when I finally went back to do my advanced, and they realised me and another guy had never been assessed. When I started you didn't have to be assessed, just turn up. Don't worry about small mistakes, unless it collapses round your ears you will pass, I have yet to meet a man who failed this.