Make parts of a block model turn on and off with nbt tags

I wand to make a block that connects to other blocks so i added one NBT tag for each direction (up, down, east, west, north, south) and now i want parts of the block model to turn on and of with these NBT tags just like how mojang does it with fences and glass / iron bars. can you tell me how to do it? im using blockbench for 3d models.