A ridge board connects the two gabled peaks. It's basically a just a 42' long 2x4. Okay, 2x4s don't actually come that long so it's really three boards joined together. You can see one of the connecting splints near the right of the pic below. Since they are glued and screwed together it may as well be one big board.
In that pic I'm cross nailing the top of the last rafter into the other splint. The tops of each rafter are double cross screwed into the ridge board. This is one of those places where I prefer screws over nails. They grip so much better. The trick was having a solid platform (thanks, decking) upon which a good stepladder (thanks, FIL) allowed me to safely put my weight into the driver. Otherwise, if you've ever tried to drive 3-1/2" deck screws then you know the care it takes to not strip out the screw head or driver bit. Still, there's something satisfying about sinking a big nail by hand so I like to do so once in a while. That's why in this pic I'm swinging a hammer while a perfectly good driver hangs in my tool belt. Just in case you were wondering.
A purlin is just like a girt but for the roof instead of a wall. So they bridge across rafters instead of studs. Their purpose is the same since steel panels for the roof and walls are the same. Well, except for color in my case.
In addition to purlins on top, the gabled ends of the building needed some angled girts. That's where the steel siding will stop.
The steel roofing went on in two days. I screwed down the last panel today.
There is quite a bit of trim work left to be done. But if it rains now the decking should stay about 98.6 percent dry.