GB/T 3903.39-2008 is a test standard for the peel strength between the upper layers of footwear. It is suitable for all kinds of upper materials, and the firmness of the bonding between the upper layers is evaluated through specified test methods. The standard clarifies the test principle and details the required equipment, such as Tensile machine. The preparation of the sample, including size requirements, sampling parts, etc., also specifies the specific test steps and result calculation methods. This standard provides a unified and scientific basis for the mass control of the upper surface of footwear, which helps to improve the overall quality of footwear products.