You might be wondering what is a stretch wrapper. Well, it's a person that by hand, wraps a stretchable plastic film around products stacked on a pallet. A stretch wrap machine does the same think but without the need for a person to walk in circles around a pallet.
Also known as a skid wrapper, the most common kind of machine uses a rotating turntable and a stationary tower to which a cradle holding a roll of stretch film is mounted. The turntable turns on a horizontal axis while the cradle holding the roll of film moves up and down on a vertical axis.
The plastic is attached to the pallet by wedging it between two products stacked on the pallet or by tying the film to the pallet itself. When the pallet turns and the film rises, it has the effect of encapsulating the stacked products in the stretchable plastic. Additional encapsulation happens when the film lowers back to the bottom of the pallet. Tension placed on the film causes it to remain tight around the products. This is known as load containment force. It's what keeps the pallet together while being moved around your warehouse or while on a truck en-route to its final destination.