This is a multi-school, leveled skill.
The purpose of this skill is not yet known. Possibly related to Structure repair?
I haven't kept any data on this (yet) but I have a CP I maintain with no cornerstone. Ever since I bought Structure Repair 1 + 2 on a bored whim, the costs seem to have been reduced (i.e. at 90% it used to cost 2 flax/straw + ~40 bricks now it costs 1 flax/straw + ~30 bricks). - Noobiehotep
Structure repair is used for attempting to repair the things inside a compound that have fallen into disrepair when the compound dropped to 0% protection. - AmisiBastet