Since 1.0 fences attach to adjacent blocks. Since 1.1, netherrack fences do too. This mod just makes fences behave like they used to, for aesthetic reasons for maps built before that change was made (see the last two images for why I made it). With the mod, they only attach to other fences and gates.
This is purely for aesthetics, for maps built before the fence change if those maps assumed and made use of the old style fences. I’ll probably make it configurable, or per map or something in the future.