[ Solved ] How to properly add transparent textures?

Good day, I am trying to add some rails with some enemies behind them but the parts which are supposed to be empty are black instead. What am I doing wrong? I'm using the midgrate texture by teh way.

You can't use transparent textures on solid walls for transparency- only linedefs with sectors facing each side!

See this article, and especially the pictures in the "level structure" section.

3 hours ago, FuzzballFox said:

You can't use transparent textures on solid walls for transparency- only linedefs with sectors facing each side!

I changed the texture using linedefs mode.

3 hours ago, Gez said:

See this article, and especially the pictures in the "level structure" section.

That wasn't helpful. Here's a better view, maybe this is more understandable.

What are the floor and ceiling heights for both sectors?

Because I see that you have a lower texture on the back sidedef here, which is the one facing the large room. And the upper and lower textures will always be opaque. Try to change the sector heights so that they have the same floor and ceiling heights and it should be transparent.

5 minutes ago, Gez said:

Try to change the sector heights so that they have the same floor and ceiling heights and it should be transparent.

That did it. I only had to change the ceiling height. Thanks.