An example of a sudden jump in height of the border.
It is noticeable in this image that the border between spirals runs perfectly horizontal on the left before suddenly jumping up on the right. This has been interpreted by Peter Rockwell as showing that carving was done in place and started before all the column drums were set up. At this point the carvers were waiting for the next drum to be put up before they could continue. When it was put in place they continue upwards. Support for this proposition is provided by the fact that the carvers appear not to have been able to cross over the block line on the left, resulting in a number of squashed figures.