Abstract: A method of assembling a heart valve is provided for use with an inner and a spreadable outer stent. The outer stent is mounted onto a spreading tool including a spreading ring, and expander, and a plunger. A protective cap is placed over the outer stent and plunger to prevent relative rotation of the outer stent to the expander prior to the complete spreading of the outer stent. The inner stent, with tissue wrapped thereon, is mounted onto an insertion tool including a mandrel having a plurality of guide rails for mating with slots of the spreading ring, wherein the guide rails in the slots provide axial and radial alignment of the inner and outer stents. The mandrel holding the inner stent is inserted through the spreading ring holding the outer stent, thereby releasing the mated stents from the spreading ring and mandrel and securely clamping the tissue between the stents.