Depending on what angle the vehicle is on.
parked facing down hill to the right: Fine no leaks at all
parked facing down hill straight : slight leak drivers side
parked facing down hill to the left: the whole windscreen
parked facing up hill whole back half of the cab.
solution only park in a garage.
this is of course just a joke.
I have a small leak above driver between the windscreen and roof. This only started in the last 10,000 or so km's up till then it was perfect. Even then it is only a small amount of water and only when it rains hard something this side of Aus (apart from Syd) has not had for a while. It's a Dec 99 with 90,000 on the clock it was a minning vehicle before I bought it so it did spend a lot of time off road.
Adam