Book belt

It occured to me that the nylon belts used for car seatbelts are strong and under tension would make excelent shelving if made about twice to three times as wide. Of course it wouldn't have to be black either.

How it would work is you have a fixed end attached to the wall, and a movable end attached by several parallel belts each a suitable distance apart for holding books. The mobile end is pulled out as far as required and then locked in placeby first tugging sharply to "lock" the belts and then pulling it tight. Some kind of ratchet to pull the shelves tight would help. A break is then inserted holding the shelves in this position and the books can then be loaded onto the shelves.

To extend the shelves, unload and pull out some more belt from the fixed end before relocking. to contract unload and allow the belts to recloil. You'd have to take the books off to change the length of the shelf but at least it should be quick to adjust and it can pack into a very small space when not in use.