Teeth have a hard surface layer called enamel.

牙齿有一层叫做釉质的坚硬表层。

Lay a sheet of wax paper on a hard surface.

在坚实的平面上摊一层蜡纸。

The hard surface is one key factor of urban heat effect.

硬化路面是城市热环境效应影响因素中较为重要的一个因素。

Applied on all resilient floor and hard surface which need to wax.

所有需要打蜡的弹性或硬质地面。

It made it more slippery with the sand on top of the hard surface.

由于赛道表面有很多沙子，显得比较滑。