Anybody out there got an idea what could be used as a good fence or rail around outside of layout board that's shape is a large U approximately 45 ft. outside dia. ? Something 5"-6" wide--(tall). Material needs to be flexible enough to go around a 30" dia. I have tried "gutter guard" but did not work.
What's the purpose of the fence/rail? Are you trying to keep the trains in, or the people out? Does transparency matter?
There are a number of transparent plastic sheet options, most easily fastened to the edge of the layout, that will achieve both goals while still allowing full visibility. There are also simple landscaping and fencing options that mostly allow visibility while restraining wayward rolling stock. Here's a couple of simple examples at one corner of my layout:
I used 1/8th inch hardboard and coffee stirrers to fashion and hot glue together a 'safety rail' on the el loop above, while using dowels and steel wire as a "catch fence" on the O-27 corner curve below. Both can effectively restrain any derailed rolling stock, while IMHO not being too visually obtrusive or obviously non-prototypical.