When siding your home, especially in wetter climates like the PNW, it’s important to apply proper rain and snow protection to your siding. As you can see in the photos above the bottom trim piece, there is a sheet of Z metal that prevents water from entering the gap between the trim and wall sheeting. On the top of the T-111 you can see there is a bead of caulk run on top of the sheeting, preventing water from seeping down the gap and rotting the siding away. The final layer of protection is provided by running the shingles past the edge of the T-111; aiding in the shedding of water and snow.