Hello. (´・ω・`)
Currently a pakset can have only one fence and slope.
But I think they have different appearances depending on the times.
Sometimes it creates weird mismatches because the buildings change from age to age but they do not.
For example, a green iron fence in ancient era or exposed slope below skyscraper.
For example, create the following and set them to intro_year:
Wooden fence, white painted wooden fence, iron fence
Bare slope, stone wall, brick slope, concrete slope
Adding them to the pakset is much easier than drawing a single building.
If the pakset author doesn't want to do that, it's still fine. This is just an option.