checking your rear beam is striaght

[dub-disaster]

just wondered what was the best method of;
 a.) Checking the rear beam is straight
b.) lining the rear beam up straight to go back on the car - i know four wheel alinment is porbably the best but are there any methods that i can do as apposed to taking it to a to a garage
i only ask as when setting up the castor on my subframe my wheelbase was different on each side of the car do wanted to check everything was reasonably straight at the back before i started measuring from it.

[scotsjohn]

Not a lot can go wrong with the rear end unless the car's been in a shunt. You'd probably have to get an optical check on it to be really sure. The front end's prone to throwing up odd measurements though. It doesn't take much of a knock to bugger things up and what you're seeing is pretty common. Not very scientific, but I just took my measurements from the rear of the door frames and it looks and feels OK.