Just for information if your TIU is mounted in a difficult to see location such as under the layout, these boards can be remote mounted in something like the example project cases shown below. They are 80 x 46 x 17 mm inside dimensions, and will just nicely fit one or two indicator boards. These can then be mounted on your control panel, facia, or wherever is handy.
They come in lots of 10 and my cost including shipping to AZ was about $21.
Rod