This tutorial covers a few extra locations I've found for defending the second point of the first defensive round of pl_Goldrush. I would only recommend doing this if you are not the only engineer on your team since; this makes a good backup plan for defending point B if your team loses the first point. To start off you're going to need to make your way to here:
Then build a dispenser at the the bottom of the slope - opposite the stairs:
Now once that has started, jump onto the dispenser and crouch jump onto the top of the slope. (You don't have to wait for the dispenser to finish)
It's best to destroy the dispenser at this point, you're going to need it for building.
From here it's your choice on where you want to build;
And you're done! Make sure to build a teleporter to this spot and keep it protected, since this spot can give advantages to other classes as well.
Thanks for reading!