A key patterned arm

Bain regularly used this design from the Aberlemno cross-slab. It is a great example of using key pattern to fill a shaped space. He focuses on it in his introduction to the key pattern section in his book Celtic Art, Methods of Construction. He also uses it to show how inaccurate other published drawings of the design had been. Clearly he had quite a ‘bee in his bonnet’ about these errors.

In the annotation of the drawing he gives his notation for describing the design numerically.  This is not easy to understand, especially when the underlying grid system for laying out the design is not shown.  Nowhere in his book does Bain ever clearly explain the notation.