Step 1

Attach the Ledger Boards
Attach 2 x 6 ledger boards to the corner posts of the tree fort.
Step 2

Drill Holes in the Boards
Use 2 x 4 blocks to flush the board with the angle brace. Use clamps to hold it temporarily in place. Use a heavy-duty 1/2" hammer drill with a long auger bit to drill the holes.
Step 3

Attach the Board to the Tree
To attach the 4 x 6 ledger board to tree , first make sure it will be level. Stretch the board from the tree fort to the tree, level the board and make a mark with a hammer and prybar on the tree where the top of the ledger board needs to go. Pre-drill holes in the tree. Attach the board to the tree using 10" galvanized lag screws.
Step 4
Smooth Any Rough Edges
Lift the 4 x 6 bridge spans into place, and sue a router or belt sander to smooth any rough edges on the lumber.
Step 5
Secure the Beams
Secure the beams to the tree fort with carriage bolts.
Step 6

Attach the Planks
Rough cut the planks to go across the bridge. Leave the planks uneven for the classic "treehouse" look. Attach planks to bridge spans.
Step 7
Secure the Rail and Ladder
Secure the ladder to the bridge with lag screws. Attach the rope rail from the tree fort to the tree for extra security.