Adjustable shelving
An adjustable shelf is a shelf that can be adjusted according to needs. The most common variant is that the height intervals can be adjusted to accommodate various items. This allows more flexible use to hold items of value for storage, display or sale. Like fixed shelves, the horizontal planes are normally made of strong materials such as wood or steel (occasionally glass or other materials), but their exact vertical positioning can be varied - usually through the use of uprights into which supporting brackets or the shelves themselves can be fixed at different heights.

For example, in furniture such as a cabinet or bookcase, the vertical elements may be drilled to allow metal or plastic supports to be inserted, and the shelf then rests on the supports. Alternative approaches include the use of grooves on the uprights at either end of the shelf into which the shelf can be inserted.

Adjustable shelves are available in many variants. Pallet racks are some of the toughest adjustable shelves, and can withstand very high loads of up to several tonnes.

History
Seeking a more flexible and reusable alternative to wooden shelving to store paper and other consumables in his London-based printing business, engineer Demetrius Comino invented the slotted angle steel construction system, Dexion, and began production in 1947. This quickly became popular internationally for domestic and commercial shelving, warehouse pallet racking and other purposes. Dexion and other shelving and racking brands are still marketed by the Norwegian Constructor Group.

The Dexion-style slotted angle or angle iron was also widely copied by other manufacturers using different configurations of slots, different metal thicknesses, and different metals (e.g.: aluminum).

Application
Purpose-built adjustable shelving systems can be fixed from a wall and/or be floor-standing.

 Common wall-fixed systems comprise parallel metal strips (attached to the wall by screws) which have slots into which brackets can be fitted to hold shelves.
 Free-standing shelf frames are also usually manufactured from metal (usually steel), though the shelves may be made of wood. The metal frames may be formed of slotted angle - steel strips longitudinally pressed into a right-angle or L-shaped section (C- and box-section systems are also used where structures have to carry particularly heavy loads); these sections are perforated with circular holes or elongated slots to allow shelves to be mounted directly or fixed using nuts and bolts. The most heavy duty form of adjustable shelving is pallet racking.

See also 
 32 mm cabinetmaking system, standardised mounting method which allows interval adjustment of furniture shelves, supports, drawer slides and hinges
 Eurobox, system of reusable containers for transport and storage in standardised sizes
 Floating shelf
 French cleat, modular way of securing objects to a wall, e.g. for adjustable shelving
 Preferred metric sizes

References

Furniture
Warehouses
Cabinets (furniture)