How to name my options when switching a line between ‘topleft to bottomright’ and ‘topright to bottomleft’

So i have an editor that can draw lines, and in this editor the user needs to be able to choose between a line that draws from 'topleft to bottomright' OR 'topright to bottomleft'. So visually it would look like a '/' or '\'.

How would i name these two options? And what would be the best way to do this? A radio button? Or a button that switches value?