Start on all fours with your hands directly under your shoulders and your knees directly under your hips.
Keep your right knee at a 90-degree angle as you slowly open your left leg to the left until it is parallel to the ground. Your weight should be evenly distrubuted and should not shift over to the right side; both hips should be square toward the floor. Be sure to keep your arms extended throughout the entire movement.
With control, lower your leg back to the starting position.