irregular cut with pull command

[seti1973]

hi guys, first of all, I introduce myself, I am juseppe, neo-written and neo cadddist for hobby. I used with "success" the command draws by defining 3 points. Now instead the same command determines me in a section of the same design 3d an irregular cut creating a solid "sbieco" compared to the base plane (quota 0 I call it). in the drawing that I attach it is those portions of solid trapetidals that expose to the 4 corners.
How can I do that?

the autocad version is 2009

 

[lattu]

I don't understand your request.
explain yourself better, thanks