The rafter table and the outside edge of the back of the square, both on
body and tongue, are in twelfths. The inch marks may represent inches or
feet, and the twelfth marks may represent twelfths of an inch or
twelfths of a foot (that is, inches) as a scale. The rafter table is
used in connection with the marks and figures on the outside edge of the
square.
At the left end of the table are figures representing the _run_, the
_rise_ and the _pitch_.
In the first column the figures are all 12, which may be used as 12
inches or 12 feet, and they represent a _run_ of 12.
The second column of figures is to represent various _rises_.
The third column of figures in fractions represents the various
_pitches_.