How can I use /fill or /setblock to change an entire door without destroying either part of it? (1.16.5)

Question

I'm trying to replace the top half of the door with a trap door and the bottom with another trap door of a different type.

The problem though, is that one segment of the door always seems to break, even if /fill is used. Using /fill to make it all air or all of one trap door type and then switching it over doesn't work either.

I've tried about 20 different combinations of command block/position orders and nothing seems to work.

Answer 1

You can use the /fill command like this to complete this:

/fill <starting block> <ending block> <blockname> 0 replace <block to replace>

That then should simply replace the block you inserted at the end.