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 equipment rental company United Rentals (NYSE: URI) jumped as much as 11.4% this morning on about double the average trading volume.

So what: United Rentals' second quarter wasn't terribly impressive, as the company missed Wall Street expectations on both the top and bottom lines. That would normally send a stock plunging rather than soaring, but profit margins are improving and management talked up the second-half prospects convincingly enough to light a fire under the stock.

Now what: The company is optimizing its customer mix and fleet expansions to "create demand for our equipment now and in the long term," all as part of a plan to remove United Rentals from the weak and unpredictable construction market. Moreover, management is tapping into low-interest financial markets by selling $500 million of new debt notes this week. Despite United Rentals' claims of controlling its own fate in spite of a soft market, investors are taking this report as a positive sign for construction specialists: Rival RSC Holdings (NYSE: RRR) rose nearly 5% on the news while equipment builder Manitowoc (NYSE: MTW), and even mighty Caterpillar (NYSE: CAT), are posting modest gains on a generally down market day.

Interested in more info on United Rentals? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.