Well if we message you then no one else gets to benefit from the answer. So here are some ideas.
How about a bag of oranges? If the bag is cut right, it could make a nice construction fence.
Or perhaps mesh drywall tape? OGR member Serows1 made a fence out of this. See this link and scroll near the bottom.
https://ogrforum.ogaugerr.com/...9#144734384881016709
For the security gate, I assume you mean a chain link fence with a rolling gate? You can buy them. Traindame here on OGR has kits.
https://www.twtrainworxstore.c...hain-link-fence-kit/
You could probably make one too, Search for "Chain Link Fence" and have fun reading all of the different ways members make theirs.
Have Fun!
Ron