Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of H&E Equipment Services (Nasdaq: HEES) fell as much as 10% earlier today, ending the day still down 8% after heavy selling. Clearly somebody is very upset because ...

So what: That's really all I've got for you, folks. Because what? I do not know. It's been nearly a week since H&E reported earnings, so that bad news is already out there. The company hasn't filed anything significant with the Securities and Exchange Commission today, either. Really, there's no news to speak of that could explain the drop, unless ...

Now what: We cast our eyes farther afield, and examine what's happening at companies like H&E. What we find here is that rival Hertz Global Holdings (NYSE: HTZ) announced today it's considering a spinoff of its equipment rental business as a means of raising cash to help it buy Dollar Thrifty Automotive (NYSE: DTG). Hertz further said it is considering "other options" for disposing of its unwanted unit. And while this is total speculation, I wonder if perhaps someone has caught wind that one option might be selling the unit to H&E at too high a price?

I don't know this for a fact. Heck, I don't even know this for a rumor. But if a badly priced acquisition turns out to be either fact or rumor, it might help to explain what's going on with H&E's stock price.

What is really going on with H&E Equipment Services? Add it to your watchlist. As soon as we know, you'll know.

Fool contributor Rich Smith does not own shares of, nor is he short, any company named above. The Motley Fool has a disclosure policy. Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.