Prone

The prone position is when one lies on the ground belly-down. While prone, a player can crawl underneath certain obstacles that a crouching or standing player cannot.

In-game, the player receives the most weapon accuracy, but suffers from a lack of mobility.

Proning has been a feature of every Battlefield game with the exceptions of Battlefield: Bad Company and Bad Company 2.

Battlefield 3
that a player can use the prone position to make use of a weapon's bipod, giving in-game justification for increased accuracy.