Expensive books and big books are all wrapped in plastic bags or letters and then put down, that is, folded horizontally. Cheap books, books that are often turned over are all vertical. The purpose of the library is to arrange and consult the books by sticking them up and standing them upright. But if it takes a long time, the book will turn yellow and be covered with mud. It's hard to clean. When you go to the ancient books department or the place where used books are sold, you will know that all the boxes are lying down. Then you can put a note on the box, write down the title of the book, or search it. The only problem with horizontal placement is to consider the same size. If the big book is below and the small book is above, it will leave a mark on the cover of the big book after being exposed to the sun (or light), or it will fall on the cover of the big book. So, try to wrap it in paper without words (mimeographed words may stain the book) and lie down. You can also write the name of the book on paper. When the book is long (maybe more than 750px thick), it is best to put it vertically. There are many benefits. First of all, books vary in size. When you put them horizontally, you should consider how to stack them. Too many books will add weight. At the same time, the friction between books will cause you to take out unnecessary books when you pick them up. More importantly, you should rearrange it after reading it several times, provided that you don't like messy things, and at the same time, it is more convenient to read, especially when you are looking for long topics or uncommon words. You can read what you like when there are few books, especially when there are few commonly used books (such as homework). You can stack them horizontally at the corner of the table, which is beautiful, neat and convenient. Of course, if you are a civil servant, reading vertically and the leader reading horizontally, it will be easier for you to pick up. If it is to protect books, of course, it is vertical. I believe you haven't seen many libraries put books on the shelves horizontally.