If you've ever wondered what it looks like to encounter grazing fire in an actual gunfight, this video is about as close as you can get to seeing it without experiencing it.
The footage, which was recorded by members of the Free Syrian Army in 2013 near Aziz, shows a gunfight over open and flat terrain. We can see the FSA utilizing micro-terrain and concealment to safeguard their firing positions, but once the SAA catches onto where they are the fire starts coming in hot and heavy. If you watch closely, you'll see tracers start to skip across the screen. It's important to remember for that every one tracer you see, there's another 4 rounds flying through the air that you can't.
Militarily, grazing fire is defined as fire approximately parallel to the ground where the center of the cone of fire does not rise above the average height of a man. Depending on which publication you look at, the exact number for which grazing fire occurs can be between 1 meter and 1.8 meters. When each bullet is fired, it will leave the barrel of the weapon at the axis of bore set from the angle of sight desired to strike the target area. The trajectory of the round should be constant as well as maximum ordinate. Maximum ordinate is the highest point of the trajectory, which is usually two-thirds the distance to the target from the weapon. Depending on the caliber of the round being fired and the slope of the terrain, as well as the distance to the target, the bullet will maintain a semi-flat trajectory.
When achieved properly, grazing fire is devastating to infantry troops in the advance or retreat. It fixes the infantry in place and makes it very easy to exploit them with other combined arms weapon systems such as artillery, indirect fires such as rifle launched grenades, and close air support. It's a key aspect of the combined arms conundrum.