If you take long/short exposure in indexes, for example buy YM and short NQ, then you can trade (roughly) three times the size in notional amount using the exchange variance margin (SPAN). ***This is stuff like having $2,500,000 in long DOW contracts and short $2,064,303 in the NASDAQ (you are risk adjusting exposures so that the overall risk of the trade is lessened). [many times a pro trader has to manage exposure, but a perfect hedge is unavailable, so they use cross hedges] this could be stuff like hedging out the commodities risk in stock (british petroleum, royal dutch shell, etc) position by selling crude oil futures. This is a cross hedge that is long stock and short commodities to cut the overall risk while still earning the dividend from one of the supermajors. ***Technically, this is a cross hedge. However, you can trade this position like a market maker by initiating the position just before a large move, or inside a range that is being traded in. You can be long and short equities at the same time and just be adjusting the net exposure. So if you think the market is bullish, you get neutral or net long (while still holding significant positions). If it's ranging, you act like an MM and scalp legs at the ranges. Likewise, when conditions breakdown you adjust to be neutral or net short. Here is something to think about. Imagine you're a pro trader that has no exposure at 5:00AM and your boss tells you to get a list of exposures going in the UK and US equities markets in order to hedge a portfolio of (long/short) stock holdings and to not fuck this up. You also have to deal with all kinds of ad hoc shit all day like filling client positions and getting positions on at VWAP or better. You are going to need to be A LOT BETTER AT TRADING than just picking entry, take profit, and stop loss.