The boxes come with 1/2 inch openings in each end of the box and one in the back. It also comes with plugs.
I used 1/4 x 1 1/2 in bolts and 1/4 in x 1 1/4 washers to mount the boxes to the strut through the 1/2 knock out in the back of the box. I "ass"umed the washer inside, covering the hole, would make a seal tight enough to keep water out. I was wrong. After just a year the outlet failed.
It turned out that the top box with the switch was full of water to the level of the bottom lip of the box. It also was full of mildew.
Are the plugs that come with the box supposed to be water proof without using any sealer? Would it be a good idea to drill weep holes in the bottom of the boxes to let any water out? Does a washer in the back of the box make a water tight seal?
I plan on redoing the boxes and sealing the openings at the top and back, but is sure didn't seem necessary at the time.