1. Check the product's delivery certificate, pay attention to the delivery date, specifications, company name and production license number. 

2. Look carefully at the surface condition of the product. The product should be bright in color, and there should be no obvious scrape, bubbles and other defects on the surface. 

3. The thickness of the product shall be noted. The product thickness of the door and window material should be no less than 1.0mm. 

4. Pay attention to the thickness of the surface coating of the product. The film thickness of the anode oxidation product is not less than 10μm, the film thickness of the electrophoretic paint product is not less than 17μm, the coating thickness sprayed by the powder coating is not more than 40-120μm, and the fluorocarbon coating product should be painted with more than two layers, with thickness no less than 30μm. 

5. Users in coastal areas choose electrophoretic paint profiles, powder coating profiles or fluorocarbon spraying profiles with good corrosion resistance. 

6. Other hard objects such as brushes cannot be used as the cleaning tool for routine maintenance. The soft cotton yarn and cotton cloth shall be selected. 

7. Water, detergent and soap can be used for cleaning, instead of other organics.