I don't know if I've got such a great mind. Thanks for the compliment though. LoL I probably go into too much detail because I figure a lot of people don't realize what's involved to fabricate some of the big stuff.
You use a lot of dogs and wedges fitting vessels. Wedges are used for the heavy jobs like fitting 2 1/2" thick heads. Most times you can just weld on one side like in your picture but sometimes you have to weld both sides and grind one weld out to break it off. Really heavy jobs need hydraulic porta-powers to put things in place.
I worked in a vessel shop that had a 10' diameter, 2 3/4" head weighing over 10 tons fall off and partially crush a wire feeder. It put a hole in the concrete floor as well. A lot of wedges were used to fit it and it was fully tacked in place for the root pass but must have been under a lot of stress. Tacking isn't really the right term. When fitting thick vessels you lay a piece of round bar in the bevel and put a weld down each side so you don't burn the edge for your root pass. The round bar is 1" to 1 1/2" long and you put a 1/4" gap rod between the 2 bevels for 100% penetration. We heard a ping, then another ping and it didn't take long to realize the tacks were breaking. It was almost like slow motion, then BANG! We saw the wire feeder and XMT 304 cart sitting there but you don't take chances with a 10 ton chunk of steel making strange noises. The tacks were about 6" apart all the way around! I helped fit it back on and got to do the MIG root pass. Had to use a tiger torch to preheat it but man that was a lot of grinding! You start your root pass between the tacks and grind out and clean up every piece of round bar as you go. You also have to feather your root pass every time you stop. Once the root pass is done you grind all your stops and starts and run a 3/16" 7018 hot pass so hopefully the sub-arc won't burn through. Fixing sub-arc burn through for 100% X-Ray isn't fun and neither is grinding off all the welds from the wedges. LoL
For pulling checker plate up on skids when they're upside down, we just used a piece of pipe with about a 2" wide flat bar on the end. In that case you tack the back side of the flat bar on the checker plate and place the other end on the I beam. Then just use the weld as a hinge and pull the checker plate up and tack it in place. Pull the pipe handle back and it breaks the tack so you can move to a new location. Very fast and because the tacks are on the bottom and nobody see's them, you don't normally have to grind them off.