flat jewel cylindrical hole for detent

例句：

1. 1. The floor is flat and easy to clean.
   地板是平坦的，容易清洁。
2. 2. The table is flat and perfect for a presentation.
   桌子是平坦的，非常适合做演示。
3. 3. The cake is flat and delicious.
   蛋糕是平坦的，美味可口。