Then I used a marker and drew a line down the approximate center to the hand rail:
Then using a box cutter I cut along the line I drew on the heat shrink. To make sure I did not cut into the handrail this was done after removing the heat shrink from the handrails:
Now I could poke the hand rail through the opening I just cut. I would then just use the cutter and trim around the handrail stanchions so that I would be able to have a pattern that would enable for me to place both side of the heat shrink under the handrail:
It worked ok but, it was difficult to exactly cut the pattern right and took a longer time than I expected. Plus dealing with a 90 inch strip of shrink wrap was a little unwieldy. So for the other hand rail I came up with a better plan. I cut small pieces of the heat shrink into sizes that would fit under the space between the stanchions instead of one long 90 inch strip:
This was much faster and easier to install. All I had to do was tape around the stanchions to secure the heat shrink and protect those areas from drips. This was much better and easier than my original plan. I was still recycling some of the shrink wrap and could reuse the patches I cut next time too. So even though my first idea did not work as good as I thought it would be. I did find a better way that saves on tape use, still protects the deck and recycles some the heat shrink plastic at the same time.