We've all experienced the dreaded cogitus interruptus: you're in the middle of a complicated spreadsheet or a delicately worded proposal or just plain thinking (in the words of Jack Handy) deep thoughts. Just when you're about to have your Eureka! moment, someone taps you on the shoulder or sticks his head into your office and says, "Dan, got a sec? Just a quck question. . . " (which, of course, never is). And just like that, you've lost your train of thought, and with it, the cure for cancer, the recipe for transmuting lead into gold, or the angle for getting the company to pay for your boondoggle of a trip to Paris. In today's open offices -- and with the near-universal belief in an open door policy -- it's getting increasingly difficult to find time to work without interruptions. What can you do?

A company I know has a totally open floor plan. They don't have any offices, and the cube walls are low -- about chest height -- so there's no privacy. They've found a simple solution: each person has made two paper signs. A green sign (made with green highlighter) says "open," which means they're available to talk. A red sign has a time written on it -- in other words, "do not disturb until ___ o'clock."

It's cheap, it works, and it keeps you sane. Think about it. (Without interruption.)