Hello,
This mitre box only has a cutting angle of 45° and 90°. So it can cut straight across horizontally, or at an angel horizontally.
However, it would not be able to cut vertically (180°)
You would likely need a table saw/circular saw or similar tool for cutting decking boards vertically
Thanks for using Q&A. [DG]
Answered by: DGIFF
Date published: 2020-07-21