Measure and cut the 10-foot, 2-by-8 board to 9 feet with the circular saw. Repeat with the 10-foot, 2-by-4 board. Cut the remaining 2-by-8 board into two 35-inch pieces. Sand all the edges smooth with the palm sander.
Measure and mark with a pencil 2 1/4 inches down from one edge on each 35-inch piece of wood. These pieces are the uprights that will be cemented into the ground. The measurements are for making the notches to hold the pipe.
Use the hole saw to make a 2 1/4-inch hole in each marked board. The marking made earlier shows where the bottom of the hole is. Use the jigsaw to cut out the remaining wood and create the notches. You will end up with a U-shaped opening on each board.
Find the center of the 2-by-4 board. Cut a U-shaped notch on this board using a 1 1/4-inch hole saw, with the hole bottom being 1 1/4-inch from the edge of the board. This board is the brace board for the seat of the seesaw.
Dig the holes for the uprights, using the post hole digger or shovel. Secure the uprights into place, with the notches facing each other, with the fast-drying cement. Leave 18 inches of upright sticking out of the ground, with a spacing of 7 3/4 inches between them.
Make a line down the center of the 9-foot, 2-by-8 board. Place a bead of construction adhesive along this line. Place the brace board on this line, with the notched side down, making a closed hole. Let dry.
Turn the board over so the seat side is facing up. Reinforce the bracing by inserting screws every six inches with the drill and a screw bit.
Turn the board over again so the bracing is facing up. Slide the pipe through the notch and center it, with about 1 1/2 inches of overhang on each side. Secure the pipe into place with the pipe straps.
Make two marks at each end of the board, with the seat side facing up. These marks are 16 inches from the end and 1 1/4 inches from each side. Drill out the marks with a drill bit that is slightly larger than the marine rope. This is for the handles.
Thread the marine rope through the holes, as if you were sewing. Knot the open end. Pull five or six inches of rope through the top to make the handle. Cut the rope and knot the end. Repeat for the other side.
Drill 1/4-inch holes in the uprights above the notches. These holes travel through the wider part of the board, and will need a long drill bit to make them. This is where the metal dowel will go to serve as a locking pin for the seesaw.
Place the seesaw seat board onto the notches of the uprights. Slide the metal dowel into place on each side. The seesaw is now ready to use.