Definition of «to smooth the surface»

The phrase "to smooth the surface" means to make something flat, even, or free from roughness or bumps.

If you travel on smooth surfaces then this will not be as important. (greatplainsexaminer.com)
A big smooth surface of black is really hard. (rivetedstudio.com)
The original foam was still in ok shape and it provides a very smooth surface for the fabric to lay on giving the finished product a «professional» look. (celebratingeverydaylife.com)
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