How do I make the outline of a wall invisible?

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These are beam walls located at GL -1200.
1. What method should I use to make the lower wall invisible?

a. Home only

b. Display order down
c.

d. ????

2. But if I use c, I would like to know how to make it appear on the screen again.

3, I divided the lower floor wall into two parts, one of which was covered by a slab and expressed as a hidden line, and the other was the same wall, but I wanted it to be shown as an elevation line, so I divided the wall into two parts and handled it like this. Is there another way?