Can an American explain to my what's with the grooves on PS1 NTSC cases?

Submitted ⁨⁨1⁩ ⁨week⁩ ago⁩ by ⁨eru777@lemmy.world⁩ to ⁨games@lemmy.world⁩

https://lemmy.world/pictrs/image/fdec3a0f-d06f-4d0c-9f96-810ee4b19d92.jpeg