In trading on Wednesday, shares of the iShares 10-20 Year Treasury Bond ETF ( TLH) entered into oversold territory, changing hands as low as $138.9301 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of iShares 10-20 Year Treasury Bond, the RSI reading has hit 25.0 — by comparison, the RSI reading for the S&P 500 is currently 52.1. A bullish investor could look at TLH's 25.0 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), TLH's low point in its 52 week range is $132.87 per share, with $148.75 as the 52 week high point — that compares with a last trade of $139.06. iShares 10-20 Year Treasury Bond shares are currently trading off about 1.1% on the day.