Detail of the Sebasteion panel depicting Io and Argos.
The arm of the righthand figure in this image shows that some alteration of the size and position of these figures was undertaken during the carving process. The pair of outlines along the side of the arm show that the whole relief was initially roughed-out and then the background was flattened with the tooth chisel up to the roughed-out figures. When detailed carving began on the figures their sizes were reduced, hence the discrepancy between where the arm finished and the flat background begins. This shows that roughing-out was followed by background work and then carving on the figures, a different approach to that seen on certain monuments in Rome, notably the Column of Trajan, on which the figures were largely finished before the background was dealt with.