Thanks, mitcorb
what if my shape isn't periodic like stairs? what if it has an arbitrary shapes with different hights?
Thanks.

Hi All,
I'm new to SketchUp and new here at this forum. I'm facing a problem I couldn't find an answer to. I'm trying to add a layer above all the structure I built, and I want it to follow the topography. Lets say for example, I have stairs and I want to cover them with some layer (e.g. deck or rubber). I would like to know if it's possible to do it without selecting each face seperately. Also, i would be happy to know how to do it: 1. only on the top faces. 2. on the top and on the side faces.
I hope I made myself clear enough.
Thanks.