Legendary fund manager Peter Lynch said that you shouldn't invest in any idea you couldn't illustrate with a crayon.

I'm not much for crayons, but I do love the pithiness of that line. It's something we regularly preach at the Fool: Don't buy what you don't understand. And if you can't simply sketch out a company's business model -- how it, you know, actually makes money -- then maybe you shouldn't be investing in it.

Today I'd like to share a very simple visual of one of my own portfolio holdings, the surgical robot pioneer Intuitive Surgical (Nasdaq: ISRG). Here's my attempt to encapsulate the company's business model:

Disagree with me? Think I missed something? General thoughts on this exercise? I'll be reading the comments below, so please share. And if you haven't already, be sure to follow Intuitive Surgical using the Fool's free new My Watchlist tool.