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 gypsum products maker USG (NYSE: USG) jumped as much as 10.8% in heavy morning action.

So what: Investors are heaving a huge sigh of relief as strong Black Friday retail sales seem to signal that the purse strings of Americans are finally loosening up. USG is a global business but more than half of its sales come from domestic buyers -- mainly through largest distribution partner Home Depot (NYSE: HD). Hence, the American retail climate has an outsized effect on this company's prospects.

Now what: Mind you, it's a bit early to call a turnaround for USG at this point. The company is swimming in debt and burning cash quarter by quarter, and is trading at a measly 0.3 times trailing sales for good reason. But Berkshire Hathaway (NYSE: BRK-B) guru Warren Buffett owns a big stake in the company, and he rarely bets big on surefire losers. USG may deserve a second look, but wouldn't exactly take out a second mortgage in order to finance a big buy here.

Interested in more info about USG? Click here to add it to My Watchlist.