Step 1: Determine the Placement of the Obstacle Course

Old tires can be obtained from tire-recycling centers, tire stores and junkyards. Look for tires that are all close to the same size. Before you begin, thoroughly clean and degrease the tires.

Use spray paint to mark a reference line on the ground for the position of launch deck, tire ladder, obstacle wall and landing deck.

Step 2: Set Up the Launch Deck Posts

Use a posthole digger to dig the four holes for the 4" x 4" launch deck posts. The holes should form a 24" x 7' rectangle. Place the 4" x 4" posts in the holes and fill with fast-setting concrete. Use a level to plumb the posts.

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Step 3: Attach Rim Joists

Mark the 4" x 4" posts 18" up from the ground. Make sure these lines are all level as this is where the rim joists will be attached to the posts. Measure and cut 2" x 6" rim joists to length for sides and ends. Position, level and attach the rim joists with galvanized screws and lag bolts. Cut the excess height off the 4" x 4" posts so that they are flush with rim joists.

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Step 4: Attach the Center Joist

Using joist hangers, install a single 2" x 6" center joist that runs the length of the launch deck. This will help support the decking boards.

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Step 5: Attach the Decking

Using 3" galvanized screws, attach 5/4" decking boards on top of the launch deck frame, laying the boards perpendicular to the center joist and rim joists. You may need to rip the last decking board lengthwise to get a perfect fit. It is okay if the boards hang over the edge. To trim the overhanging deck boards, snap a chalk line on the ends of the planks and use a circular saw to cut them flush.

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Step 6: Set the Obstacle Wall Posts

Use a posthole digger to dig the three holes for the 4" x 4" obstacle wall posts. The holes should be parallel with the launch deck, with the two outside posts aligning with the outer edges of the launch deck. Center the third post between the outer two. The posts should be placed approximately 8' from the launch deck. Place the 4" x 4" posts in the holes and fill with fast-setting concrete. Use a level to plumb the posts.

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Step 7: Attach the Wall Boards

Measure up 4' from the ground on one of the posts and use a square to draw a horizontal reference line. Measure and cut a 2" x 6" board to the width of the wall. Position the board at the reference mark and attach it to the post with 3" galvanized screws. Cut and attach 2" x 6" boards all the way to ground level. Cut the excess height off the 4" x 4" posts. Install a 2" x 6" top board on the opposite side of the obstacle wall. Install a 2" x 6" top cap after the tire ladder is installed.

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Step 8: Build the Gravel Pit

Construct the 5' x 8' gravel pit frame using 2" x 6" boards. Connect the sides and end boards with butt joints. The obstacle wall makes up the fourth side of the gravel pit frame. Attach the two side pieces to the back of the obstacle wall. Using a staple gun, install landscaping mesh to prevent weeds from growing up through the gravel. To cushion the wooden edges of the box, glue foam pipe insulation along the top edges of the 2" x 6" boards. Fill the pit with pea gravel.

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Step 9: Assemble the Tire Ladder

Drill holes in the tire treads and connect a row of three tires, using galvanized bolts, nuts and washers. Repeat the process to create two more identical rows. On one of the sets of tires, drill holes that will accept the steel cable. On each tire, drill two sets of two holes opposite each other. Repeat the process on one other set of tires. Drill some drainage holes to let rainwater escape. Thread the cable through the holes, leaving at least 18" of cable extending from both ends. Attach the ends to the first two eyelets on the obstacle wall using cable clamps. Attach the opposite ends of the cables to the launch deck. Repeat the process for the second set of tires. Lift the center section of tires into place and connect them to the outside rows with bolts and washers.

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