Link between Categories and Products tables

[tcv]

I am using a trial version of Able Commerce 7.0 Asp.NET 2.0 Shopping cart.
In the AbleCommerce database I am trying to figure out how the "ac_Categories" and "ac_Products" tables are linked with each other. In ac_Products table there is no foreign key to ac_categories table. I did not see any bridge table like "ac_ProductCategories either. Can any body let me know how these two tables are related?

Thanks

[jmestep]

The link is in the ac_CatalogNodes table.