Certain products require a specialized storage medium. Cantilever racks have arms that allow the storage of long awkward products such as tubular steel, pipes, and lumber. Furniture and boat companies are good examples where the cantilever rack is widely used.

This type of storage medium presents unique challenges to a WMS. Locations defined by the smallest product volume or length to maximize storage capacity. As the product size varies and requires more than one consecutive location for storage, the WMS must have the ability to assign multiple locations to the one product based on the location and product size parameters. Since the directed put-away logic can get complex, an alternative approach is to allow the operator to determine the storage location for the inventory, referred to as assisted put-away.

Cantilever rack permits a FIFO product rotation, excellent storage density, and excellent product accessibility. The unit-load position has a utilization factor of 85 percent and handles a high volume.

Pigeon-hole Rack

These are made of angle-iron and the bars or tubes are stored in them horizontally. They can be built as hi8gh as handling facilities allow, will hold large quantities of material and are, therefore, fairly economical of space. They have two main disadvantages. Firstly, it is not possible to load or unload them mechanically and manual labor must be used, and secondly, there must be sufficient clear space in front of the rack to allow the longest bars to be put in or taken out. These racks are best used for bulk stocks.

Metal Plate and Sheet

Large quantities of metal plate are best dealt with by simple floor storage and the same way may apply to sheet, although sheet is often kept on pallets if the size is suitable. Sometimes, however, where stocks are not extensive, it may be desirable to have specially designed racks for these materials.

Light plate or sheet can be stored horizontally or vertically in a rectangular angle-iron framework, but this arrangement allows manual handling only. Heavier items can be accommodated vertically in a rack made of two steel joists or channels along the floor with uprights of ‘A’ frames at intervals to act as spacers.

One incidental advantage of this method is that, if steel plate is kept outside, vertical storage allows the rain to drain off quickly and minimizes corrosion. Where mechanical handling is necessary for heavy plate, the best method is to use a crane with a special attachment known as a plate clamp, which can be fixed on the edge of the plate to allow it to be lifted.