How to properly cut the outer (outer) corner on a plinth or baguette, without tools?

How to cut a baguette (plinth) without a miter box if you have an external (outer) angle of 90 °. This video shows an example of how to first mark up a baguette, and then cut it off. For clarity and ease of perception of the process, the action is moved from the ceiling to the floor, but the rule itself is still the same. ----------------- ---------------------------------------------- Musical composition "Abracadabra" by Silent Partner