Shimozami was a subordinate of gate watcher serving at Mitsuke (area lying outside the gates of a castle) in Edo. They distinguished passing processions which came to castle.
There was a rule that Gate watchers returned salute to passing processions depending on kakaku (family status) and positions.
To prepare for that, gate watchers had to identify the leader of processions quickly, therefore a specialist job, shimozami was created to distinguish processions.
Skilled Shimozami could identify whose processions they were instantly at a glance from a long distance.
In her own story included in Kasshiyawa written by Seizan MATSURA, she wrote that shimozami recognized the lord of Matsuura domain and responded appropriately though they just rode away in an urgent situation, unlike normal procession.