Sanding bag
![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f9/BU-56_Illaminako_Ateak_02.jpg/220px-BU-56_Illaminako_Ateak_02.jpg)
Cavers with grinding bags in front of the Illaminako Ateak cave in Navarre
The sanding bag is part of the equipment of speleologists . It is a very robust, waterproof backpack , which, as the name suggests, can easily be pulled along the ground in the narrow cave passages.