The hamstring stretch is a basic static stretching exercise to improve flexibility.
Sit on the ground with your legs extended and hands planted on the floor just behind your hips with a slight bend in the elbows. Bend one knee and bring the heel toward the opposite inner thigh. This is your starting position.
Lean forward and grab the toe of your extended leg, feeling the stretch in your hamstring. Hold, return to starting position to repeat on the other side.
Avoid pushing yourself to the point of pain. You should feel a bit of mild discomfort, but not pain.