When you fight Bloch,the first shot he fires is at the catwalk above.
The rocket makes it fall(but it's still hanging by 4 wires). You keep
shooting him until he goes to the 3rd level of the catwalks on the
sides. He'll go through the hatch. Refill your Q-Jet and use it to get
on the catwalk that he blew up. Go to the top of it until you reach
the 3rd level railing. Turn arround so you can see the hatch that
opened,then use your Q-Claw on the "grate" to pull yourself
up.

  When you get through just walk foward. You will pick up a
MRL-22 (Rocket Launcher),shoot him with it and a cutscene will appear
and the game will have been BEATEN!!!!

   P.S.It's eayser than it sounds.