1. Scrape the width of the gap with a putty knife and scrape it into a figure of eight, which is wide outside and narrow inside.
2. Fill the gap with gypsum block dry powder. The filling depth is not less than 3-4mm, and it is 1-1.5mm lower than the wall surface.
3. Brush the gap with 18 glue and stick a glass cloth or cowhide note.
4. Scrape 821 putty for 2-3 times and smooth it with the original wall, and then polish it with sandpaper.
5. Adjust the wall paint. After the paint is adjusted, brush the sample first. After drying, compare it with the wall color. The color is close, and the color difference is not big. Then brush the wall.