To form the bale, the material to be baled (which is often hay or straw) in the windrow is lifted by tines in the baler's reel. This material is then packed into the bale chamber, which runs the length of one side of the baler (normally the right hand side when viewed from the front) in offset balers. Balers like Hesston models use an in-line system where the hay goes straight through from the pickup to the flake chamber to the plunger and bale-forming chamber. A combination plunger and knife move back and forth in the front of this chamber, with the knife closing the door into the bale chamber as it moves backwards. The plunger and knife are attached to a heavy asymmetrical flywheel to provide extra force as they pack the bales. A measuring devicenormally a spiked wheel that is turned by the emerging balesmeasures the amount of material that is being compressed and, at the appropriate length it triggers the knotters that wrap the twine around the bale and tie it off. As the next bale is formed the tied one is driven out of the rear of the baling chamber, where it can either drop to the ground, or be sent to a wagon towed behind the baler. When a wagon is used, the bale may be lifted by hand from the chamber by a worker on the wagon who stacks the bales on the wagon, or the bale may be propelled into the wagon by a mechanism on the baler, commonly either a "thrower" (parallel high-speed drive belts which throw the bale into the wagon) or a "kicker" (mechanical arm which throws the bale into the wagon). In the case of a thrower or kicker, the wagon has high walls on the left, right, and back sides, and a short wall on the front side, to contain the randomly piled bales. This process continues as long as there is material to be baled, and twine to tie it with.
