Unfortunately I trusted when marking the holes of the built-in spirit level. Upshot was that my 46-inch TV hung low on one side by about 1 cm and can be clearly seen. The built-in level was simply wrong mounted in the holder. So rather take their own, long spirit level, if you do not it is to drill more holes than necessary.
Another problem is the insertion of the safety rail after mounting. You should make sure to have enough free space left or right next to the TV. By ultra-slim form of the holder of the TV rather dense hanging on the wall and it is not easy to slide the rail into the slots provided.