Answer:
What kind of room has no windows or doors?
The stack just might be sent all over. Full of what's new, yet it's nearly obsolete.
who do you think you know but sometimes you don't
Runs smoother than any rhyme, loves to fall but cannot climb!
I'm not man's best friend, I'm their enemy, I can mark your end, yet you do not see me, I am very small, but very tough, If you have me, then you have it rough.
You use it between your head and your toes, the more it works the thinner it grows.