My possibilities for U didn’t inspire me at all — usage? uniformity? — then this morning while Tam Lin and I were out walking, “undo” popped into my head. (This is why W is going to be for Walking. Coming up soon! Watch this space.)

My next thought was “Doesn’t undo begin with Z?”

Muwahahaha. If you’re a Windows user who writes and/or edits for a living, you are almost certainly on a first-name basis with CTRL+Z, the keyboard command that will undo most of the awful things you just did. No, it will not bring back the document you accidentally trashed before you’d saved it, but after you’ve done that once, you’ll probably remember to name and save new files as soon as you create them, and tell your PC to automatically back up your work at regular intervals.

If you decide that the awful thing you just undid isn’t so awful after all, CTRL+Y will bring it back. I don’t use CTRL+Y nearly as often as I use CTRL+Z. That probably says more about me than I want generally known, but there it is.

Aside for Mac users: The Mac equivalent is COMMAND+Z. To undo your undo, it’s COMMAND+SHIFT+Z. I can’t verify this at home, but you can if you’ve got a Mac.

CTRL+Z is so much easier than its analog predecessors: erasers, Wite-Out, correction tape, etc. With those methods, undoing your undo was pretty much out of the question. And don’t get me started on correcting a master stencil in the heyday of mimeograph. In case you’re wondering why I wax rhapsodic about CTRL+Z.

If you use Track Changes — as I do when I’m editing, all the time, but not so often when I’m writing — it’s easy to flip back and forth between the original version and whatever you did to it. Even so, CTRL+Z saves my butt on a regular basis.

But really, people, this isn’t just about a handy keyboard shortcut. It’s a reminder that — at least until something’s published, and maybe even then — you can change it, rethink it, revise it.

CTRL+Z is a reminder that you’ve always got an escape hatch, a safety net. Feel free to take risks. Don’t worry about looking stupid to yourself 10 minutes later. You can always undo it.

And if you decide you had it right the first time, you can undo your undo.