In trading on Monday, shares of the Guggenheim BulletShares 2021 High Yield Corporate Bond ETF ( BSJL) entered into oversold territory, changing hands as low as $24.8175 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 Guggenheim BulletShares 2021 High Yield Corporate Bond, the RSI reading has hit 29.7 — by comparison, the RSI reading for the S&P 500 is currently 42.3. A bullish investor could look at BSJL's 29.7 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), BSJL's low point in its 52 week range is $23.77 per share, with $26.41 as the 52 week high point — that compares with a last trade of $24.82. Guggenheim BulletShares 2021 High Yield Corporate Bond shares are currently trading down about 0.4% on the day.