I was told many years ago by an old craftsman that the diamonds were for
gauging wallpaper as each mark represented a rolls width. This was back it
the days before the wallpaper came pre-trim to width.
They're for spacing things five to the 8' panel. Usually, studs are
16" on center (the red marks), or 6 per 8'. The black diamonds are 5
per 8', and every two feet makes 4 per 8'.
The down side of 5 per 8' is that you don't have anything at the 4'
mark so you can't alternate your 4x8 panels like you do with 16"
spacing. You'd have to use a different pattern.
In general, the red diamonds are 16" apart, allowing 4 studs (and
three spaces) to support a 4' sheet of ply or drywall.
And the black ones are about 19.2", allowing six studs (five spaces)
to support an 8' sheet. (This is primarily used in commercial work,
where steel studs are used to hold long sheets -- 12' and longer -- of
It's also the spacing on the pre-fab wood trusses holding up
the roof of my addition, because the engineer at the truss plant
said we needed that _or_ 2x6 top chords to make the trusses
stiff enough that the ceiling drywall wouldn't crack, so I said
"Over-built" (like "over-kill") is an oxymoron. :-)
Dennis M. O'Connor email@example.com
I just love to hear the replies when someone asks this question. Everyone
has a different opinion. And it's interesting to see the uses by the guys
who didn't have a clue and came up with their own uses.
It is a framing mark, and it is used as a layout for certain trussing, I
used them in school for Truss-joist systems.
"Violin playing and Woodworking are similar, it takes plenty of money,
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