How can I fold #ifdef/#ifndef blocks in Emacs?

I want to hide blocks of #ifdef and #ifndef blocks in C. Looks like I'd either need to use Folding mode or the Outline minor mode.

How do you fold like a pro?

Fold a face-down shirt in half lengthwise. Fold both sleeves over and bring the bottom hem up to the collar. Fold the stack in half once more making a small rectangle. File them vertically in a drawer so the folded "spines" of the shirts are visible.

hide-ifdef-mode should do something like that. I have not used it myself though, but turn it on and read it's description with the commands below. It should be included with emacs.