Surface "extruding" with z axis only

[BB8x]

Hello

I have surface made from many planar surface.Lets say it is the top. I would like to copy this surface below for lets say 2 metres - orto Z only.

How to create solid from this surface entering height 2 metres? Extruding does not work - it is not keep z axis. Thinker has issue as it intersects 

Any idea how to?

[vladimir_michl · Accepted solution]

Can you just copy the surface using an offset of 0,0,-2 and then use a difference volume? See:

https://www.cadforum.cz/cadforum_en/difference-volume-3d-solid-between-two-tin-surfaces-sets-tip1105...

Vladimir Michl, www.cadstudio.cz - www.cadforum.cz

[BB8x]

My knowledge is bit better - extrude/select axis Z