I don't fully understand supply lines. I sent one settler from all of my settlements to set up a supply line heading to Sanctuary Hill. I know that my settlements can make use of the workshops from Sanctuary hill but I'm not sure if Sanctuary Hill can get stuff from the other settlements. Is it one way or two way? Also what if I have stuff from Settlement and I don't have it on Settlement B, does it transfer items through sanctuary hills or do I have to send a settler to all settlements?

Thank you.

It is two way, with a pass through ability. E.g. Like the internet, long as a settlement is hooked up to any part of your supply network, supplies are shared between all settlements connected, even if it takes multiple hops to get there.

Example) A --> B, and A --> C
Settlement A has supply line to B, and another supply line to C
All three settlements share common inventory because each city has at least one 'road network' it can send/receive materials from
E.g. C gets stuff from B via routing B --> A --> C

ONLY raw parts are sent via supply lines, finished products are not - so not everything is shared via supply line. Steel, wood, and screws for example are shared - furniture and guns you built and stored at one settlement are not shared. Seeds like corn and tatos are shared, plants you already planted then stored are not shared. Basically, all the parts you use to make things are shared, all the finished products are not.

Thanks a lot man.

Just noticed my newer route not joining up with the main network due to a lot of settlements being at the cap. Wish it was easier to see where the suppliers are going so you can connect the ones not already joined to the main

Go to the pip-boy map, press C (on the PC) to show trade routes.

that should show you where everyone is going.

Yeah, I do that but it's a case of tracing the lines to see if they meet up with somewhere on the main route. Would be great if when you hover over the line or settlement it blinks where they are supplying. Probably easier if I just reassign some people from sanctuary