Wall and door repair is a healing skill. I discovered it because my Sentinel of Rkugamz set would spawn a dwemer spider everytime i repaired. So i tried to lay down a Extended Ritual to get minor mending (thanks to the passive) and suddently i repaired for 300 more health every repair. My base repair is 6120 and with minor mendig i repair for 6440, I dont know if it scales with magica/stamina and spell damage. Tought this was an inntresting discovery, and if you have other inntresting and random discovery, please let me know.