You should probably talk about short box spreads.

Short box trades on index options are a cheap way to borrow money, usually much cheaper than a margin loan. These are cash-settled (European style) options, so there is no risk of exercise.

Short box trades on equities are trickier. They can provide cheap money, too, but they must be monitored to avoid exercise, and if the stock falls, the strategy can produce losses beyond the risk-free rate interest rate. But that's a two-way street; a box trade on an equity is in effect a buffered, short-term investment in that equity. The spread moves in the same direction as the shares, but not as dramatically.