Things You'll Need
Two 2-by-6 pine boards, at least 11 feet each
Two 2-by-4 pine boards, at least 9 feet each
One box of 3-inch long wood screws
Power drill with screwdriver drill bit
For household projects that require a ladder, such as changing light bulbs or painting, you should buy a folding ladder, preferably an aluminum one, for convenience and safety. But if you want a permanent ladder as part of, say, a tree house or a loft, a better solution is to build one yourself out of wood. Safety and stability are the most important issues, so don't skimp on the materials or take shortcuts from the directions. These plans are for a 10-foot ladder with seven steps. You can adjust the length of the rails and the number of steps for shorter or higher ladders, but attempting to build your own ladder beyond 12 feet tall isn't recommended.
Lay the two 2-by-6 boards on a flat surface and, with your tri-square and pencil, mark a straight line across the width of the boards, about two inches from the bottom of each. Cut the ends even with your circular saw so you have a clean right angle to start with. Then, with your tape measure, mark both boards 10 feet from the newly cut ends. Mark straight cross lines at those marks and cut them.
Turn one of the newly cut 10-by-6 boards on its narrow side, so the 2-inch width is facing up. With your tape measure and pencil, put a mark 16 inches from the bottom end of the board, then another mark 16 inches from that and so on until you've put seven marks. The top mark will be eight inches from the top of the board. Use you tri-square to put straight lines across the width of the board at each mark. Repeat for the second board.
Lay one of the 2-by-4 boards on a flat surface. Use your tri-square to mark a straight line near the bottom, and use your circular saw to cut it clean. Then measure exactly two feet from newly cut bottom, put a mark, and use the tri-square to draw a straight line there. Use your circular saw to cut the line so you have a two-foot-long piece of 2-by-4.
Repeat the process for the rest of the 2-by-4 board, cutting four two-foot long pieces out of it. Then repeat the process on the second 2-by-4 board to cut three more two-foot pieces, for a total of seven.
Lay the two 2-by-6 pieces on their narrow edges, parallel to one another, about two feet apart. Take one of the two-foot pieces of 2-by-4 and lay it on across the parallel boards, with the edge of the short piece lining up with the lowest lines on the long pieces.
Standing above the boards, use your power drill to put three screws into the face of the 2-by-4 and down into the narrow side of the 2-by-6. The end of the 2-by-4 should be flush with the outside of the 2-by-6. The screws should be lined up in a straight line. Repeat on the other end of the 2-by-4, screwing it into the other 2-by-6.
Position the second 2-by-4 piece at the next lines on the two 2-by-6 pieces and screw it in. Repeat for each of the seven steps, moving up the lengths of the 2-by-6s. The tops of the 2-by-4s will be 16 inches apart, with the top step eight inches from the top of the long rails. Secure the ladder to your tree house or loft with screws.
If your ladder is going to lean in at an angle, you can use your tri-square and circular saw to trim the bottom of the 2-by-6 rails at an angle so it sits flat.
Always wear eye protection when using a circular saw