Background and approximator placement
Place the background material underneath both vessels. Now ligate the femoral artery in close proximity to the intersection with the inferior epigastric vessels.
Hold open a single vascular clamp with your clamp applying forceps from a caudal direction and place the most proximal segment of dissected vein in between the clamp arms. Give both vessels some time to dilate. Set the distance of the approximator clamps to match the length of the dissected femoral vessels.
Place the approximator on the vein at a small distance from the intersection with the inferior epigastric vessels and on the artery at a small distance from the inguinal ligament. Leave enough space proximal and distal to the approximator for flipping it over.