How to make edges like this

so i want to make edge like i mark with red line. how? using knife tool feels weird. here screenshot when i try knife tool :frowning:

You can do this with tinycad addon and the VTX function: https://docs.blender.org/manual/fr/dev/addons/mesh/tinycad.html

let me try, i’ll update the result. thank you for your answers!