Clipping tool cause holes

Garry's Mod mapping
#1

when I used clipping tool on my “ground” and ran my map, I saw this:

http://img405.imageshack.us/img405/3340/screenkratka.png

Pls help

#2

Those are displacements right?

#3

Have only the top face selected when you make a displacement.

#4

and next time go here