Rail Placement Fix is a Minecraft mod that allows you to place rails more precisely. By sneaking and looking at the corner of a block, you can place curved rails or place sloped rails like a top-side slab. This mod enables you to create any rail pattern you like without changing the shape of neighboring rails.
Must be installed on the server to work in multiplayer. For usage in singleplayer worlds the mod has to be installed on the client.
.jar file into the mods folder of your Minecraft directory.