What is a Short Sell Against the Box. A short sell against the box is the act of short selling securities that you already own. This results in a neutral position where your gains in a stock are equal to the losses. [or, when you buy warrants for cheaper than the market price, and short the current PPS, you lock in “free money”... even better if the stock pumps 1-3x right before you short. It’s a very old, and very obvious strategy, to those who know what they’re looking at -ed.]

From: https://www.investopedia.com/terms/s/sellagainstthebox.asp