Stap 6 vertalen
Back of the PCB. The metal tab you see sticking out of the boards towards the middle is connected to the metal shielding shown in the earlier steps (step 3).
As you can see, there is a lot of unused space on the board, specifically on the bottom left. There are a few reasons for that,mainly due to there is mains (120v +) in that general location, and as a safety concern only necessary traces go there. In most of todays electronics you see what is called a "ground power" or a "power plane". Instead of having traces for ground and power, they use the empty space on the board for copper connected to ground or power. It helps immensely in power distribution and a ground plane is often necessary in high speed electronics for proper current return.