Hi, i tried to stamp a curved road profile on the terrain and it worked nice. You can draw a centerline for your road profile, divide it, drop it on the surface, using follow me or the road profile builder extension you can create main road shape, and stamp it to the surface..
So, everyone knows about this, i thought i am the one who found it.. 
I don’t really know when were sandbox tools added to SketchUp, but it’s been there since I started using it ~2009
“I don’t really know when were sandbox tools added to SketchUp”
Sandbox Tools were added in SketchUp 6.
yeah, it’s the main diff between stamp and drape. drape will just project the contours on the terrain.
stamp will take the bottom face, no matter if it’s flat or not, and make the terrain adapt to it
good tool for swimming pools too
I use sketchup almost since google buys it and i have never seen a video or tutorial about using stamp on curved surfaces.. It is perfect for creating roads on terrain. People usually drape the lines on the surface and paint with asphalt texture. There is paid plugins for creating roads and stamp tool makes better jobs than them. I asked some professionals and they said stamp will raise the terrain as flat plane.. They thought this function is a new uptade to the sandbox tool..
Using Make 2017
I know all versions can do it. Have you ever used it before? I mean, we did’nt know because we never tried..
Regularly.