Any thoughts or good experience using...

never heard of it. What does it do (look) like? Does it sit tangent to the curvature of the Earth?

I have seen them in person, very nice tool.
It has everything you'd ever want on it for figuring out layouts of rafters.
Here is a link:
http://www.foxmaple.com/chappellsquarepr.html

Also:
http://www.chappellsquare.com/

And a pdf, might have to put that on the tool list.

http://www.foxmaple.com/Chappell_Sq_Bklt.3.pdf

As I work outside almost exclusively, and often with oak, the stainless steel aspect is great! Add to that the fact that all scales are in sixteenths, and you have a winner. The unique tables just add to the wonder. As soon as I can find the $180, I am buying the enitre set.

I didn't notice markings in 16ths. I work in 1/16", 1/8", 1/4" etc., sometimes even in schquarters, but never in tenths or twentieths.

All the squares I've used until this one had 12ths and tenths. And while these have their place, I am often frustrated during layout when I find I am marking something other than a sixteenth. So unless you are doing a lot of stairbuilding or scaling plans with your square, not having to deal with these odd scales is worth the money in itself.

I suppose after using it for a while and following the conversion chart, on the square, you would accept the 20th scale. Might be a hump that would need hurdling.

And it will still work after the EMP goes off.

As to decimals, Steve Chappell once told me he likes to do all design calculation in decimals, converting only to fractions (if necessary) at the very end.

Although I am a traditionalist and love fractional systems for their embedded humanity, I have indeed learned that in successive and cumulative calculations rounding errors are introduced by fractional calculators. These can then produce mystifying inaccuracies, especially in cutting braces etc.

Therefore I suppose a decimal square would help allow direct application of decimal measurement.

I once had crew member introduce a square with tenths on one side and eighths on the other, but we didn't notice at first. An abomination. Caused endless aggravation until we cut it up into pieces.

Dave, is a "schquarter" the same as four-shtinkz?

Pete

A schquarter is 1 1/4"