Trex RainEscapeWall Flashing 1/4" X 1" X 25'

The material is too stiff! There's not enough compressibility to ensure a tight and complete seal along the entire length of the board. Adding insult to injury, the adhesive strip would barely adhere to anything and the rubber strip would come lose from the board edge at the slightest touch from anything. Overpriced, over-rated, and completely useless from my experience with it.

The name of the game in building decks, especially if hung off an exterior wall, is keep wet debris away from siding. This stuff does that well. It makes for an excellent treatment for the boundary between planks and exterior wall surfaces. Some gaps will occur, but giving water a place to drain to and keeping significant debris from holding water against a wall surface, be it wood or other material, will go a long way to preventing dry-rot in places where rain (or sprinklers) will get to. The adhesive side is meant to hold the tape in place while you put down boards. It won't hold the tape in for a long period of time, so don't put it down and think you'll get to it a day later. Further, it will not cope well with dirty surfaces. Don't even think about using tacks or staples on it. They will pull right through the material. Deck board edges will hold the tape in place long term.