Instructions for how to hammer in a nail
Diagram showing the direction in which to hammer the nail.
Strike nail firmly and repeatedly at this location until end is flush w/ surface of wood (note: use hammer)
Hold nail firmly as this location w/ hand not used on hammer handle.
Important: install nail pointy end first
Caution: remove fingers prior to complete installation of nail.
This is the least funny xkcd comic.
You just don't understand it.
In that case, I know just the place!
I found it funny before it was cool.
Impossible. By severely breaking the laws of space, time and causality, XKCD became cool across the entire universe 12 years before Randall drew the first strip.