How do you know when you are at max angle on the trailer?

SDcampowneroperator wrote:
Put a strip of tape or some other marker on the trailer that you can see in your mirror when you get to the danger point.

Simple. I like it.

I was thinking of putting tape on the trailer triangle and looking in the rear camera for it but this is better.

I can simply keep looking at the mirror and when the tape is about to vanish behind the truck: It's going to hit.