ribbing
US /ˈrɪb.ɪŋ/
UK /ˈrɪb.ɪŋ/

1.
a series of ribs or ridges, especially in fabric or a structure
:
•
The sweater had a distinct vertical ribbing.
•
The concrete structure featured strong steel ribbing for support.
a series of ribs or ridges, especially in fabric or a structure