Which color should this room be? A Painting Hack

We're having the first floor of our house painted, and the guys who are doing it have obviously been doing this for years. They need a minimum of instruction and just get efficiently to work.

I made an appearance to help show them which type of paint when into which room. Rather than depend on me putting the right paint cans in the right spot, or remembering anything, the guy in charge scribbled on the wall appropriate color number. And what fancy tool did he use to accomplish this? A plain old quarter.

The chances that they'll apply the wrong color are now much slimmer.

There's just something about watching folks who know what they are really, truly, doing. Whether it's a programmer, car mechanic, chef, Doctor or anyone else...the hacks that they use are almost a work of art.