Lattice is commonly used to cover the sides of decks. It is made of crisscrossed slats with small spaces between them. This design hides the underside of the deck but still allows air to pass through. Lattice also keeps out small animals that might try nesting under the deck. Lattice can be made of wood, plastic or composite. Lattice is purely aesthetic; it is too flimsy to provide any structural benefit, and must attached to the existing deck framework.
A more structurally strong method of finishing the sides of a deck is to apply solid planks to the framing. This method makes it appear that the deck is sitting on a solid foundation, so it is more suitable for decks that are lower to the ground. Planks can be made of wood, plastic or composite materials. The strips can be applied horizontally or vertically to the deck framing.
Plywood can be used to skirt a deck quite easily, but exterior or marine-grade plywood should be used for resistance to rot. If the deck sits high off the ground, providing substantial space below, applying plywood to the sides of the deck structure can create a secure storage space. Cut a door panel from the plywood, then apply hinges, a latch and a lock.
If your deck is attached to a log cabin, shed, or other rustic structure, you may want to maintain the rustic look by skirting the deck with logs. By using small logs and splitting them down the middle, you can reduce the amount of wood you need, and construct the skirting out of material that might otherwise be wasted.