Install Header Boards
With the uprights secure, work can begin attaching the header boards to the posts. These 2x12 boards are attached to either side of the posts to help support the arbor. Measure and mark the correct length of each beam, and cut them to length using a circular saw. Secure the beams to the posts using 3 1/2" decking screws. Note: Although the patio has a slight slope away from the house for drainage, the arbor roof should be installed so that it's level. Therefore, check to be sure that the header boards are level as you install them. This will give the proper appearance to the arbor and a level reference for installation of cabinets and cabinet tops.