The reference is split into the shared base modules that power all regions, followed by the region-specific packages that tailor steel sections, databases, factories, and checks to each code.

Base modules

1. sections — Provides the SectionType enumerations plus the abstract BaseSection. Every concrete section class inherits the helpers (get_properties, list_properties, from_dictionary) so consumers can enumerate attributes consistently.
2. database — The new SectionDatabase page (02-database.md) explains how JSON datasets are auto-discovered, cached, and exposed through fuzzy search, comparison filtering, and similarity helpers for resilient designation lookups.
3. factory — SectionFactory maps the cached data to region-aware section classes, auto-loading UK/EU/US modules and warning when a region does not yet have a concrete implementation.
4. checks — Limit-state helpers live here so they can be shared by multiple regions; current helpers cover ULS/stability (UK) and LRFD/classification (US), while other regions can plug in their variants.

Regions

1. UK
2. EU
3. US and US_Metric
4. IN

Each region still provides its own sections, database, factory, and checks modules. Check the corresponding regional README files (linked from the guide pages) to see exactly which standards and section profiles are currently packaged.