Back in the day the David Allen Company would sell physical products like planners, file folder systems, inboxes, etc. One of the last things I bought from them before they stopped selling physical products was their ORANGE mesh travel folder system.
It consists of the following folders:
- IN – Your mobile inbox just like in your office at home and work.
- TO OFFICE – Items that need to get back to your office.
- TO HOME – Items that need to get back to your home.
- ACTION SUPPORT – Anything that you currently physically need to complete PROJECTS or NEXT ACTIONS.
- WAITING FOR SUPPORT – Physical items or reminder notes of items you are waiting for someone else to complete.
- READ/REVIEW – Items you want to read or review while being mobile.
Based on my needs, I have added two additional folders:
- REFERENCES – Key references I want to have with me while mobile. For instance physical copies of the GTD Mastering Workflow Series Methodology Guides.
- CALENDARS/CONTRACTS – Print out of key yearly work and family/school calendars. And then a select list of phone numbers and emails I might need to reference if I don't have my phone.
These could be duplicated today with a good label printer and quality plastic file folders.
You can still get a good amount of GTD material in electronic format like planner templates, methodology guides, workflow map, etc…
Listen!
Squirrels? 
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Some Traffic Analysis
High-Level Network Diagram #1 For 2019
High-Level Network Diagram #2 For 2019
Previous WIFI Architectures (Rio)
Yuck! #1
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More Detail On Multi-Printer Attack Surfaces
Sound Damage Levels
Here are my 
Steve Holden's Blog 