1, marked during pig quarantine. Every pig must go through health quarantine before entering the slaughterhouse, and then it can be slaughtered and put into the market.

2. So for the convenience of marking, a hole will be made in the pig's ear and a qualified brand will be hung. When the pig is slaughtered, the brand will be removed, thus forming a gap.

3. So seeing such a gap shows that this pig is qualified and can be safely eaten.