Updated from 8:08 a.m. ESTThe S&P 500 is a stock tracking index that tracks the prices of 500 stocks with the largest market capitalizations trading on either the New York Stock Exchange or the Nasdaq. During the last couple of months, the index has bounced off the 800 level, and at a recent level of 845, there may be some short-squeeze opportunities with some of the stocks that make up the Index. A short squeeze takes place when short-sellers quickly buy in the stock in order to cover their bearish positions, driving the price of the stock up sharply. The ratio for measuring short-squeeze opportunities is the short ratio, which is the number of days it would take the short-sellers to cover their position based on recent average daily volume. Stockpickr has compiled a list of the top S&P 500 short-squeeze plays, including Fastenal ( FAST). To read more, visit Stockpickr.com. In Thursday trading, Fastenal closed at $34.76 per share (down 2.82% for the day; down 0.26% year-to-date). Guess Who's on Stockpickr Answers Today: Larsen Kusick will be on Stockpickr Answers today (Thursday, Jan. 29) to respond to questions and comments posed by members of the Stockpickr community. Not a member? Join the Stockpickr community today -- for free.