Festool MFS Fence System Instruction Manual page 11

Using the MFS as a large
and very accurate square.
Now matter what kind of furniture you
build, it is critical to be able to create very
accurate square components that are ex-
actly the size you want them to be. By
aligning all of the outer edges and ends
of the MFS extrusions, you form a very
accurate rectangle with close to perfect
90 degree corners.
In this photo you can see a large class 2
steel reference square placed inside the
MFS rectangle. To the right is a closer
view showing just how very square the
MFS rectangle really is.
The one shown is formed from the MFS
700 starter kit so it is 780mm by 480mm
outside. That is a square that is over 30"
by nearly 19", larger than any accurate
11
square you are likely to encounter. For
visual reference that is a one meter (39"
long) MFS extrusion in the photo to the
left.
To use the MFS extrusions as a large
square, assemble the MFS into a rectan-
gle of maximum proportions and with the
ruler marked edges facing out. This is
easily done by using a block of wood to
make sure that each end and each edge
are carefully aligned at all four corners.
Tighten down the attachment screws and
recheck to make sure you really have a
rectangle. Measure the diagonals to
make sure.
With the MFS700 shown here the diago-
nal measurement will be 915.8mm. From
high school geometry you will remember
that any right triangle has a diagonal that
is the square root of the sum of the two
sides squared. In the case of the
MFS700 the two sides are 780mm (the
700mm profile length and the 80mm ad-
joining profile width) and 480mm long.
Square those numbers, add them to-
gether and take the square root of the
sum and you should get 915.86025mm.
Before you get carried away trying to
measure the diagonals with such preci-
sion, keep in mind that one millimeter is
about .040" (forty thousands of an inch)