hi, i’ve created a surface which looks like:
__
/ h\
| |
|___|
and i want to make a hole where “h” is placed.
this hole should be triangular-shaped.
i’ve tried a tutorial that explains something about planes and separating a selection, but it doesn’t work.
how could i do it?
thank you 
Like this?
I made that by starting out with a plane, then deleting one of the verts. Then I made a edge between two of the verts so it formed a triangle. Then I added a mesh plane that was scaled larger than the triangle. Then I deleted the face from the plane, and joined my triangle hole to my plane. Then all I had to do was to fill in the faces by selecting 3 or 4 vertices and hitting the f-key. Hope this helps.
DwarvenFury
hey, thank you
i got trapped when deleting the face of the plane. how do you do it?
Choose “Only Faces” when it asks what to delete.
If it deletes all of your verts when you try to delete the face, go into edit mode, and instead of selecting the face, select one edge of the plane, and delete that particular edge, instead. To do this, go into edge select mode, select the edge you want to delete, hit the delete button, and choose Edge.
DwarvenFury
face deleted succesfully thank you