What are linedef flag effect 1, 2, 3 etc.

What does each mean. I cant find any info on the wiki and I am new to this becuase v1.9 have the name written on them instead of effect 1, 2, 3. 4. 5

I think those flags are unused now. They're just empty slots where other flags once were.

They're used for different things depending on the linedef. Effect 3 or 4 (I don't remember) on a wind or current special makes it work like a waterslide, effect 4 on water gives it the wavy effect, etc. Effect 6 doesn't seem to have a purpose, though. Couldn't it just have stayed Impassible? -_-

More complete list of flags and its usage:

http://wiki.srb2.org/wiki/Linedef#Effect_Flags_usage