Click on image to enlarge. Image is in the public domain.
The shooter places both feet flat on the ground and is bent slightly foward, so as not to lose their balance. It is important to note that elbows should not meet with the knees here (because bone-to-bone contact makes the position unstable). Instead the knees should support the muscles of the upper forearms for a stabler position. This position is somewhat more stable than the standing position, but is not as stable as some of the other positions we've studied so far. This is because there are only two contact points with the ground (the two feet) and the knees support the upper arms.
This position is NOT part of the basic US Army marksmanship course, but is used by some soldiers all the same, as well as by hunters. The advantage is that this position can be very rapidly got into and out of, from a standing position and allows one to quickly duck behind bushes, shrubs etc. Therefore, it allows the person to quickly drop out of sight and not alert the target of his/her presence. It is also useful in places where it is not possible to assume a prone or a kneeling position easily, for instance in a rice paddy field or a swamp.