Test Underdeck System and Install Gutter

What happens here

Once all underdeck panels are installed, test the system by pouring water onto the deck above. Observe the drainage beneath to ensure water flows freely towards the outer edge and drips down as intended, without leaking through the panels or connections. Before installing the final gutter, secure a section of a main rail (reversed) into the underside of the outer edge of the deck. This main rail acts as a block to prevent water from traveling backward due to capillary action, ensuring all water drips vertically from the edge. This provides a clean drip line and prepares the system for the eventual installation of a conventional gutter, if desired.

Goal: Test the installed underdeck system for proper drainage and then install a section of main rail as a backer for the gutter, blocking capillary action of water.