How to make these thumbnails?

[OfficialRutch]

Hi everyone,

I'm new to Photoshop CC 2019 and I use it for my YouTube channel to make thumbnails.

I was wondering how you can divide multiple layers with a diagonal line like in these thumbnails I attached. Many thanks for your help!

[c.pfaffenbichler]

You could use the Pen Tool (or Rectangle Tool, Ellipse Tool, …) to create white Shape Layers and apply a black Stroke to it. 

Edit: 

[OfficialRutch]

Thank you very much!

[c.pfaffenbichler]

Another Option would be creating a Shape Layer with a white Stroke and no Fill and applying the Layer Style Stroke with a black line to it. 

That might offer advantages (the thickness of the white lines could be echanged simultaneously) but also a drawback (when it contains multiple open subPathItems those get closed).