How do I fillet 2 solid bodies with radius zero?

So I am newbie to SW.  back in times I used fillet with radius zero in autocad to unit 2 lines. Now how do I do this with 2 solid bodies?

I have created an irregular piramid with 3d sketch, then surfacing it and extruding (image attached)... because I am trying to learn how to do a "prismatic surface" for my project.

Thank you

SolidworksParts And Features