FM/BG-588.V1.01 - High and low stacking
When covering corners, if one player kneels while another stands behind them, two pairs of eyes and two rifles can cover the same area, increasing effectiveness. This is commonly known as a "high/low stack" and can be employed naturally whenever the situation allows. Note that the kneeling player must not stand unless he has cleared it with the standing player - else he's likely to stand up into a bullet.
Above: 2 players using High/Low stacking to maximize fire around a corner
