Newbie question: How to reference models in subdirectories


Hi, new to RoR I am probably going to embarrass myself now:

I have models organised in subdirectories, i.e.


When I try to reference another model within the same subdirectory,
everything works fine, i.e.

belongs_to :product_categories, :class_name =>

However, when I reference a model in a different subdirectory, I get an
uninitialized constant error, i.e.

belongs_to :currencies, :class_name => ‘CrossApplications::Currency’
`const_missing’: uninitialized constant ‘CrossApplications’

What am I doing wrong here?
Thanks in advance for patience and a helpful answer!