Imagine we have 2 models

• Area
• Lane

and you want to create a standard Joins Table with just an area_id and lane_id.

When you create the table via a migration Rails will automatically create the joins table with the folloing naming convention in alphabetical order areas_lanes.

If you then decided to change the Area table to be called Screen, one of the things you will likely do is write a migration to change the areas_lanes table to be called screens_lanes.

You may think Rails will therefore look for a joins table called screens_lanes after all we have simply switched the Area table for a Screen one.

Unfortunately not, Rails will look for a table called lanes_screens becuase it will keep to its alphabetical order naming convention.

So you will need something like this:

has_and_belongs_to_many :screens, join_table: "screens_lanes"