By Jeffrey R. Kosnett, Senior Editor February 1, 2011 Suppose you just want to speculate on rising bond yields and don't care about income. No problem. You can choose from among a dozen "inverse" exchange-traded funds and notes, which rise in value when interest rates go up (and bond prices go down).The most popular inverse-bond ETF is ProShares UltraShort 20+ Year Treasury (symbol TBT). UltraShort seeks to provide twice the opposite move of a Barclays Capital long-term Treasury bond index. In other words, if the index falls 1% in a given day (meaning that yields have risen and bond prices have fallen), the ETF should climb by 2%. Conversely, if the index rises by 1%, the fund should lose 2% of its value. The problem with TBT is that single-day focus. Because the fund can only promise to achieve its objective on a daily basis and because of the quirks of compounding, you can guess correctly on rates rising but make dismayingly little money with one of these funds if you hold it for an extended period. So how do you use these critters? With extreme care. If you expect, say, an announcement of a sharp rise in employment, you could buy an inverse bond fund the day before. If you're right and the report pushes yields up, your fund will jump and you can make a quick 1% or 2%. But this isn't investing, folks. It's gambling.