Slicing at an angle

 From:  Frenchy Pilou (PILOU)
7775.2 In reply to 7775.1 
Just draw a plan (A line extruded with Direction)
and make Boolean Diff if you want 2 waterpoof objects (Option Keep Object)
or function Trim if you want Open Objects!

EDITED: 13 Dec 2015 by PILOU