This lovely and simple to use leg stretching mechanism will give you the leg flexibility needed for the most advanced martial and gymnastics techniques.  Simply sit on the ground, place the extending arms on your ankles and lean forward.  As you lean forward you will push in the center bar which further extends the extending arms that are touching your legs.  Keep your back straight as you lean forward for an even better stretch that will work your lower back as well as hip flexors and legs.