Ladder feet are in good condition, e. g. rubber tips on metal rolling ladders. "Safe-Hi" feet on extension ladders.
梯子脚底是否有很好的止滑垫片。如金属梯子脚底的橡胶，延伸梯的防滑垫片。
2
The concept of ladder plane partition is introduced which may be regarded as a natural extension of the shifted one.
作为移位平面分拆的自然拓广，本文引入了梯形平面分拆的概念。
3
The invention provides a self-locking extension working platform of a lifting working ladder, wherein the extension working platform has self-locking function.