Ten acre field of mowed hay. We mow around the outside edge of the field and work our way in, leaving concentric swaths of cut hay.
The sickle goes back and forth quickly, while the tines on the reel pull the hay towards the sickle. The sickle is made of individual blades which can be changed if they are damaged. The large metal points in front of the blades are called rock guards. They can be changed if damaged as well.
This haybine is called a mower/conditioner. The conditioning is performed by these two rolls. The hay is crushed as it passes through the rolls, allowing the stems to lose moisture faster. This helps with alfalfa, but isn’t necessary for grass.