Looking around the room, there's not much else in here except an old rusted piece of threaded rod, a dirty blue rag and some bits of thin steel wire. You could fabricate something with the items down here to start a small fire but something seems to be missing. Have you overlooked something important? Look at the other drawings to see if you can find it. Once you do, you start to assemble your flame thrower.

do we use items from the room we peered into as well? or just from this room?

Everything you would need is in this room. You will need to use the can, rod, wire, rag and one other item. You will also use two items you have found before and have in your pockets or sack that were mentioned recently.

i'm not sure how to do this. . from the hint, it looks like the rag is tied around the threaded pole, and then possibly stuffed into the pipe? but then what? someone help!

Yes, you need to cut a piece of the rag and wrap it tightly around the threaded rod on one end. Then, take the wire and secure the rag piece to the rod so you have a nice tight fit when you slide them into the pipe piece that you found next to the fuel tank. This will now act as a piston like you would find in a bike air pump. To finish the flamethrower, you need to add fuel to the open end of the pipe, then make an ignition wick using another piece fuel soaked rag stuffed into the opening of the pipe. You now have yourself a crude flamethrower that will fit into the hole in the wall leading to the lab. Let's go try it out.