Help, I can't think of the name!?

Question

What's the name of the thing that astronauts use to board rockets.

Answer 1

If you mean the structure that supports the rocket while on the launch pad and which usually has an elevator to take astronauts or cosmonauts (or taikonauts for that matter) to the level where they can access the entry hatch, then in the case of the Space Shuttle this goes by the name of the Rotating Service Structure (RSS.)  I don't know what they call it elsewhere, or what it was called during the Apollo era and earlier.  In recordings of launch communications the controllers usually say "Tower clear" or words to that effect.

Answer 2

"Gantry"