Why can't I jump at KSC

[Joeybafoey]

Whenever I try to explore the Kerbal Space Center, let's say I'm climbing up the VAB, I have to jump to begin to get over something or to get onto the next latter, but when I try to do that, it seems like I'm standing under a something right over my head. I hit space and it looks like Jeb hits his head and falls down. Is it a glitch? Am I doing something wrong? Please help.

[sal_vager]

hi Joey, when you're near the top of a ladder press F to clamber up