Why does nobody talk about the old elevator shaft trick with a laser level?

I was working on a 1970s building downtown and the foreman told me to check the guide rails with a plumb bob. He said, 'A plumb bob never lies, but it takes all day.' I tried his way, then set up my laser level just to see. The laser showed a 1/4 inch bow in the rail the plumb line missed because of air currents. Now I use both, but start with the laser to save hours. Has anyone else found old methods can miss small but important details in tall shafts?

3 comments

3 Comments

bailey.sam1mo ago

That quarter inch your laser found is probably just machine error or a shaky setup. Air currents in a shaft are a known problem, but they don't make a plumb bob lie, they just mean you have to wait for it to settle. Rushing with a laser might save time but it can also give you a false reading if it's not perfectly aligned. The old method has worked for generations because it's fundamentally reliable. New tech introduces new points of failure that a simple weight on a string doesn't have.

maxm631mo ago

Ever think about how the plumb bob line itself can stretch or twist over a long drop? That old cotton line isn't a perfect ruler... it can get a slight spiral from the weight spinning, throwing your mark off just enough to matter.

phoenixh741mo ago

Wait, you're saying a quarter inch is just machine error? That's a huge difference on a foundation or a tall wall! @bailey.sam, have you actually tried to fix something that was off by that much? It's a nightmare. A laser might have issues, but so does a spinning bob on a line that can stretch. Both methods need a careful hand.