The phrase "smooth lining" means that the inside of something is flat, even, and free from roughness or bumps.
Sentences with «smooth lining»
This groundbreaking action figure debuts a new style of construction that allows smooth lines of movement in the figure's knees and elbows. (electronictheatre.co.uk)
The design is inspired by the F - 22 stealth with smooth lines and angled surfaces. (geekwrapped.com)
It maintains an even speed and produces smooth lines for less skin irritation. (geekwrapped.com)