Here's the story... please seat your self first!!
Yes, it's my favorite restaraunt... 'nuff said :-)
When this place was built, local code required a light over the back door. That's what this light is.
A bit to the right, out of view, is the walk-in cooler. This was assembled from parts found in a scrap yard (not kidding!) and appended to the rear of the building, with a direct entry into the kitchen.
Since there was no engineering data available for this home-built cooler, the town wanted a roof over it for snow-loading purposes.
Thus, the restaraunt owners went to the handy home center, got some lumber, and cobbled together a "roof." They decided, while they were at it, to extend this roof along the rear of the building- enclosing the switchgear, water heater (gas fired), and making a storage / staging / smoking area.
There is no other roof above the chip board; that is snow that you see on it. The area near the wall is clear of snow due to a 16" overhanging eave from the 'real' roof. With the arrival of nice weather, they have laid some asphalt roll roofing over it.
The connector ("Nail plate") you ask about is made by "Simpson Strong Tie," and is commonly used here as you see. Used properly, they make quite a sturdy structure. The gang nails (rect. plates) you see connecting the vertical and horizontal wood pieces are NOT being used properly. A sharp eye will alos notice that the "rafters" are spaced too far apart and seriously undersized.