Use the 2-board expansion kit to increase the length and span of the 4-board dog pen. These kits are available with or without doors. These kits can be independently used as barriers for standard size doorways, or can be easily connected to your current dog pen to allow more configurations and larger game pens. When used in conjunction with a dog pen, you can also convert a 4-board pen into a 6-board room partition that can safely span a 121 in. W opening.