The short answer is , 3skeng is a premium professional tool. However, you can access it for free in two ways:
Getting Started with the 3skeng SketchUp Plugin While 3skeng is a professional-grade engineering extension that requires a paid annual license, you can access a of the full version to test its capabilities. There is currently no permanent free version of the software, as it is sold as a professional tool for MEP (Mechanical, Electrical, and Plumbing) and structural design. How to Access the Free Trial To start your 14-day trial, follow these steps: 3skeng plugin sketchup free
Secondary steelwork, C-channels, and duct supports. Steelwork: Structural beams and framing. The Complete Guide to 3skeng for SketchUp (Free