Test tube rack is a tool used in chemical experiments to place and secure test tubes, typically made of metal or plastic. It is designed with multiple holes or slots to accommodate test tubes of different diameters, ensuring that the test tubes remain stable and do not tilt during the experiment. The test tube rack can be vertical or horizontal, and some are equipped with adjustable clips to accommodate test tubes of different lengths. In chemistry teaching, test tube racks are helpful for students to perform reaction operations inside test tubes, facilitate observation and processing of experimental results, and maintain the cleanliness of the experimental platform. They are an indispensable basic tool in chemistry laboratories.