here), suggest that the reinforcing bars should go horizontally across the line of weakness. In reality, on a castle like Mingary, this simply isn't possible, so the first thing that stonemason Damien Summerscales has to do, after cutting the rod to length, is to chip out the mortar along the straightest path possible and then bend the bar into the resulting crack. His task is made more difficult because, if the joint between the rocks is covered with the original harling, this mustn't be removed, and even chiseling out the mortar is difficult because, although it's seven centuries old, it's still incredibly hard. The result is anything but a straight line.
Many thanks to Damien for his patience in demonstrating the process.