I'm indexing Canada, Ontario—Tax Assessment Records, 1834–1899 [Part D] [M3DR-1MX]...
You should index Thorold in the City field. It is a city of 20000. You would ignore St Patrick Ward based on the field helps that say: Do not index wards, districts, cities, or municipalities in this field.
Field helps are accessed by clicking on the purple question mark that pops up when you click on a field. They give more instructions about how to index each field.4
Thank you. I did read the field help, but must have missed that.1