This handy tool I made from two leftover pieces of MDF. I glued a sheet of sandpaper to the bottom. The vertical board is used as a hand-hold. By making the sandpaper stick out from the edges of the bottom board, it is more likely to jump onto ties that are slightly too tall, rather than just ram into them and possibly knocking them loose. I usually do several light passes as most ties are pretty much even. You can make this as long as you want it to be. The sandpaper is glued to the board with white or yellow glue, applied in a thin, even layer. When the paper wears out, I simply make a new version, as it literally takes as long as it takes glue to dry to make. The wood can be any wood, just so long as it is guaranteed to be flat. I also use this tool to sand down styrene sheet edges after cutting, or to slightly roughen up smooth styrene sheets (for better paint grip).