In the United States, a hierarchy absolutely exists in the Production Staff which is where the Assistant Director is included in both the budget as well as in the proper union – the Directors Guild of America. There are also plenty of Assistant Directors in the United States that are non-union or Independent. In other countries, an Assistant Director might be a member of the Directors Guild of Canada or a Guild in Ireland, etc.,
Here is the hierarchy in the United States:
Unit Production Manager
First Assistant Director
Second Assistant Director
Second Second Assistant Director – now this might seem an odd one. Why not just call them third Assistant Directors. Other countries actually do. The United States refers to them as “Second Seconds”.
Key Set Production Assistant