Plumb
CSI Division 05, Metals
Perfectly true vertical, the reference line gravity itself defines, which a steel column, a framed wall, or any other vertical building element has to be checked and adjusted against before it's permanently fixed in place.
Why it matters
An element that's even slightly out of plumb compounds that error as more structure gets built on top of it. Checking plumb, traditionally with a level or plumb bob and now often with a laser instrument, is a basic verification step that happens constantly throughout construction, not just once at the start.
On a real project
Before permanently bolting a steel column's base connection, an ironworker checks that the column is plumb in both directions using a level, and adjusts it with a come-along if it's off, since a column that's out of plumb now throws off every connection made to it afterward.
Who this matters most to
An Ironworker checks every column for plumb before finalizing its connection, since plumb has to be verified and corrected before the structure, not after.
Where this goes wrong
A column gets permanently bolted while slightly out of plumb, an error that seems too small to matter at the time. By the time several more stories of steel have been erected on top of it, that small initial error has compounded into a visible and expensive lean that's far harder to correct than it would have been at the start.