# creating support for a surface

I created an stl file of bathymetry using Matlab and the results can be seen in the two pictures below in Blender. The problem I have is that it is very thin with overhangs. I would like to add some kind of support. For example put a solid block underneath it like in the third picture.

I can't seem to figure out how to do this in Blender and if I try to fix the stl file in Blender it puts a surface through my original surface. I also tried to use Microsoft 3D printing repair but it takes hours to queue. How to I change my stl file so it has enough support to be printed?

• Just a note - I see you accepted an answer. It's often worth waiting to see if other answers show up; and in this case if you can add a comment indicating that this answer in fact worked for you, that will be a big help to future readers. – Carl Witthoft Jan 29 '20 at 15:52

• Select the whole ara with A
• Extrude with E then Z to constrain direction
• Scale the currently selected, extruded vertices with S then Z then 0 to force them all into the same plane