Split the tail lamp lens from the housing. This is the hardest part of the job, take it slowly and use plenty of boiling water to soften
the glue holding the lens to the housing. Gently pry the housing from the lens, using a wide flat-bladed screwdriver, pouring hot water
on the joint as you separate it. Once the parts are separated, remove as much of the glue as you can (this makes reassembly a LOT
Using the template in the picture, trace the shape of the divider onto the sheet aluminum. Cut out the divider with a pair of scissors.
Fold the tab at the dotted line to a 90 degree angle. This tab will end up sitting on the "shelf" at the top of the tail lamp housing.