Diy Christmas Light Archway . This explains my base setup. The basic idea is that the tunnel will be comprised of a series of arches. 32 Easy DIY Outdoor Christmas Lighting Hacks https//www.onechitecture from www.pinterest.com Then cut one side of the board at 2 inches and again at 3 1/2 inches. Instructional video on how to build christmas light arches over sidewalk. Step by step on how to make a lighted christmas arch.