Where do you draw the line and say, "OK, I'm actually going to print out this piece of code, spec, formula, or other info and carry it around but these pieces can stay on disk." Well, more importantly why do you draw the line there?

I've encountered this a number of times and have some sort of vague conceptions beyond "oh now I'm REALLY stuck, better print this out." I've also found some quicksheets of basic specs to be handy. Really though, I have no particular logic behind what is useful to physically have available in the design and development process.

I have a great pile of 'stuff' papers that seemed at least partially relevant at the time, but I only really use about a third of them ever and often end up wishing I had different info on hand.

Edit:

So this is what I'm hearing in a nutshell:

• Major parts of the design pattern
• Common, fairly static and prominently useful code (reference or specs)
• Some representation of data useful in collaborating or sharing with team
• Extreme cases of tough problem solving
• Overwhelmingly,almost never print anything.