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

Example:

Note
Important!
There are three Types of Joint Rules 1. By Topology, 2. by Category and 3. Direct Joints. In this order, they will be applied to the Assembly. Direct Joints will overwrite Category Rules, Category Rules will overwrite Topology Rules. See Joint Rules.
The Joints are processed first, then Features.