Setting Plumb & Square using Line-of-Sight

[Toolmaker51]

I could use a 4 or 5 way laser beam level, eventually. But currently engaged project (3 phase power) needs baselines around perimeter inside the building. Trusses, brick walls and floor obstructed by machinery already in place wasn't the ticket for my single beam. So in the past, a lot of elementary 'surveying was conducted with an 'eye-level'. Instruction book included with this Craftsman Locke Level, suggested steadying scope in a staff cut with a Vee atop. Made this one adjustable, as a can-do project, and a what-if solution. Point of origin (datum) will probably be centerline, which is all free span. From that location, an anchor will hold music or MIG welding wire under tension at the other end, 80' distant. Subsequent wires will establish the 'chalkline' for brackets supporting central trunk and each of five electrical branches.
There is some amplifying text in the JPEG, and shots to illustrate the concept as interpreted. I have not constructed a site for personal endeavors and I hope others appreciate staying in HMT vs. an external link.