Double Torsions are basically two, opposed, torsion coil bodies manufactured on one strand of wire.
These are torqued the same as single torsions. They usually center over a lever or arm and provide equal pressure on both sides. This is done to prevent excessive wear and friction that can hinder the functionality of your product and ultimately lead to failure. Other applications may require these for strength since the forces of each coil body are added together to double the exerted pressure.