s.o.s. jumping with the Keybaord (Spoilers)

[Guest7]

O.K. basic keyboarding 101 and I need help, please.

I know the Space Bar is to jump.
I can jump across, but how do you jump UP?

I am in the cave with hole in ceiling; using boxes and the large part of the ladder is already in place above.
To jump up, what is the exact keyboarding?
Like, space, w,
Or first w, then space
Only once or a few times? Go slow or fast, or does it matter?
I get to see the ladder symbol, but it doesn't stay and I go to the ground.

Also, fyi: I now have two dissapearing things. The 1st dog dissappeared (from before) and now the 2nd half of this ladder vanished from the ground.