Square set timbering is a system for supporting the rock above an area in a mine that has been emptied of valuable ore. These square sets--hollow cubes of timber--could be assembled on the surface and then fitted into place in the mine.
This development increases safety in the mine and allows greater quantities of the valuable minerals to be removed.
Miners may improve all mines to Level II. Coal and Iron mines produce four units per turn. Gold and Gem mines produce two units per turn.
