Let the Sun shine in - formerly built-over doorway.
Each one of those stones was individually carved by a stone-mason to fit the contours of its neighbours, following a drawing made by the architect's staff. Most of the stones would have the mason's mark chiselled into a face not normally visible - although some can sometimes be seen in odd stones in the museum buildings. Each "mark" is individual to the mason who shaped the stone which was an incentive to get it right first time as the mark made the stone traceable to its maker. One of the earliest forms of quality control? This would be necessary with the hundreds of thousands (maybe millions in some buildings?) of stones needing cut to precise measurements as the cathedral was erected.
Let the Sun shine in - formerly built-over doorway.
Each one of those stones was individually carved by a stone-mason to fit the contours of its neighbours, following a drawing made by the architect's staff. Most of the stones would have the mason's mark chiselled into a face not normally visible - although some can sometimes be seen in odd stones in the museum buildings. Each "mark" is individual to the mason who shaped the stone which was an incentive to get it right first time as the mark made the stone traceable to its maker. One of the earliest forms of quality control? This would be necessary with the hundreds of thousands (maybe millions in some buildings?) of stones needing cut to precise measurements as the cathedral was erected.