The Saw Guide is used for cutting Straight boards such as
risers. It can also be used to rip long 2x materials, for instance
if you have a 2 x 12 and need some 2 x 6 you can set the saw guide up on
your circular saw to 5 - 1/2 inches and
rip 2 - 2 x 6 boards out of 1 - 2 x 12.
The saw guides you get like the one in the picture will only cut widths up to 7 inches.