I have 2 Drywall T Squares, made by 2 different companies. Neither
of them is actually 48". One is 1/8" short, the other is shy by 3/16".
The problem isn't the side with the markings that start at "0" by the T
and end at 47 7/8", it's the side with the markings that start at "0" at
the end away from the T and end at 48" at the T. That first 1" marking,
(which is directly opposite the 47" marking) isn't at 1" from the end,
so none of markings on that side are accurate.
Now, I know that a Drywall T Square is not meant to be a precision
measurement device and I know how to "shift an inch" to compensate
for the incorrect marking, but I wonder why they bother to mark
the inaccurate side in the first place. If you want markings on both
sides, just start both sides at "0" by the T so that the markings line
up and are accurate.
Seems like they could just make the T squares a true 48" and eliminate
the problem. Maybe they do...both of mine were bought at the borg but
they were bought 20 years apart, so it's not a new issue.
Not a big problem, just an observation.