When Naruto and Sasuke were still training under Kakashi, they were taught chakra control by climbing trees. The basic pretense was that they need to focus chakra on their feet in order to climb high trees, not too much or it'll damage the tree bark and, not too low or you'll come falling down. A test of wits and courage, see how far high you can go climbing trees and mark your highest point with a kunai. As a challenge to Sasuke, the first one to reach the time the fastest wins the competition. A test of might and wills, see how long you can mold your chakra and how high up on the tree you can go on Sasuke Tree Climbing.