Both verticals are plumb to the wall, held steady by a rock. A corner block holds the line taut. We have to check those profiles regularly to make sure they haven’t shifted accidentally (or from silly people leaning against them). It’s essential that the wall is built on both faces simultaneously, otherwise it will not bond rightly.
Bed bonding is about the arrangement of stones across the width and length of the wall that gives structural stability. Use at least one ‘through’ stone per square yard of the wall, extending from wall face to wall face, tying both together.
Old buildings which have survived hundreds of years reflect the good workmanship of excellently bonded walls. After construction it’s impossible to tell from the face of a wall, if indeed quality bonding has been carried out. The stonemasons of old believed that God could see their work so great care was taken to bed bond.