Peering around corners while clearing a building
If you need to do a "quick peek" around a corner and don't have a mirror, have your partner provide high cover for you, get down on your knees and do the quick peek from a low level. Nearly all of the time, if a bad guy is waiting for you, he will be focused at the chest level or head waiting for you to come around the corner. They are not expecting someone to peek around the corner at ground level. Remember to always have a high cover officer in case the bad guy happens to be approaching that corner while you're doing your "quick peek."