The USA systems sometimes involves a baggage belt going along a wall, with the check in desk, which becomes more like a podium, someway forward of the belt, rather than built into the belt structure. So you check-in, if necessary the bag gets checked for size and weitght on a mini pad by the desk. You then get your baggage tags and are invited to walk forwards. This brings you to the belt, you place the bags on the belt, then turn left or right to security - at this point you are walking between the check-in desks and the belt. This allows the airport to be flexible on space and airlines. The other way to do it is with a bank of machines for self service, then once you have tagged, same thing, you walk to the continuously running belt and put your bags on it. Clearly if you screw up the bag tags, bad things will happen. I remember seeing someone clutching their tags as they walked on to the aircraft, they had put the bags on the belt, but not the labels on the bags......