Workflow
To build a timber frame Assembly, you need to:
create Beams
define Joints between these beams
define other Features (optional)
Based on this, Assembly takes care of generating the final geometry of the structure.

Example:

Note
Important!
The order in the list of Joints and Features matters! For example: if there are two different joints defined for the same pair of beams in the list, the last one will be applied (overrides entries earlier in the list).
The Joints are processed first, then Features.