What is a custom packaging box manufacturer called a plug cloth?

What is a custom packaging box manufacturer called a plug cloth?

Blocking cloth, also known as floral cloth, blocking cloth, etc. It is a processed fabric strip with edges,

Used to stick on the upper and lower ends of the spine of a hardcover book, that is, to block the cloth heads at both ends of the book back.

There are two functions:

1： It is possible to firmly adhere the book cores at both ends of the book back.

2： It can decorate the appearance of books.

What is a custom packaging box manufacturer called a plug cloth?