Quote from riskaverse305:
A bullet is the purchase of shares of stock with the purchase of an equal number of puts. Bullets were used (before the SEC did away with them) to short sell on a downtick. Since you actually "owned" the shares you could sell the stock whenever you wanted, even on a downtick. This would establish a net short position that you could trade in and out of. At the end of the day the put is exercised, covering the initial purchase. At least that's how I was told it worked. I didn't particularly care at the time, but I was new and stupid.
These days you can short to alot of ecn's (isld, arca) even on a down tick, so it doesn't really matter, just now I don't have to pay for bullets. The benefits of Reg SHO, however, seem to be balanced by its downsides. On the one hand, you can short as much fucking stock as you want. I find myself shorting far too much sometimes, because with non SHO stocks I live by the strategy of shorting when I can get it. This would be all fine and good, but the mm's play games with SHO stocks, reserve orders on both sides. It might move in the direction you thought it would, but you'll be chopped to death in the meantime.