The way in which even fine details - such as the spokes of the wheel and legs of the horses - cross the joint between column drums shows that this work must have been completed in place.
A narrow flat chisel or a channelling tool has been used to outline certain details of the horse, notably its tail and back legs, to make them stand out from the background.
Notes
In this very weathered section a certain level of damage can also be seen along this line. This might be because carving close to the edges of these blocks caused increased micro-fractures in the stone that make it more susceptible to weathering.