In this video I build a new underpass on my model railroad and try to reproduce one of the most characteristic details of blasted rock faces — the vertical marks left behind by the drilling.

Since I’ve never modelled this type of rock before, I experiment with three very different materials: air-drying clay, toilet paper soaked in diluted white glue, and joint putty from the DIY store. After comparing the results, I choose my favourite and use it to create the finished rock walls.

But there’s another important lesson behind this project: an underpass really starts when you design the benchwork. I’ll explain why I don’t consider the top of the framework to be “ground level,” and how open benchwork allows roads, rivers and railway lines to pass naturally above and below each other.

Finally, I make a simple special tool for reproducing the distinctive drilling marks and use it to complete the blasted rock faces around the underpass.