People will need to go through more than one obstacle at three places in the course: The 1/3 mark, the 1/2 mark, and the 2/3 mark.
The tires are at these spots
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The cones are at these spots
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And the hurdles are here:
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When you combine these:
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You get two marks at the 1/3, 1/2, 2/3, and Final spots (Final can be 1, 2/2, 3/3, or 6/6.)