The third of the 3 curve strokes corresponds to the horizontal stroke, and is called 平鉤 (pínggōu) in Chinese.
To form this stroke from the slanting curve stroke, 1 joint of the arm must shift position. From the previous position of the arm extending diagonally downward and outward from the body, shift the shoulder upward 45o, such that the line connecting the shoulder and the wrist is horizontal.
The arm position for this stroke is similar to the arm position for the horizontal stroke. The arm extends horizontally to the right. However, instead of the elbow being straight, it is bent downward at a 45o angle. The wrist is in line with the forearm, the palm is open, and the fingers form a hook stroke.
As an example, this stroke appears on the right side of the character for “heart”, 心.