The interface of the top wall for placing and receiving the border line is as follows:

1. Left-click to select the area or line segment where the filler is to be placed, and click the filler (The filler can only be deleted and re-placed, and cannot be directly replaced)

2. Understand the position of the sectional view in combination with the 3D view, and select the placement position of the filler according to your own needs (The filler cannot overlap with the coordinate axis, otherwise the rendering will be black);