Liners, shells or tubes, pads, build-ups, dividers, partitions and other inner packing pieces can be made in an infinite variety of ways to separate or cushion products, to strengthen the box, or to prevent product movement by filling voids. They may be simple rectangles, or scored, slotted, scored and slotted, or die-cut shapes.

Many of the types in common use have been given International Box Code numbers. The railroad Classification provides specifications for some pieces used in the packing of glassware and other fragile articles.

Pads are plain rectangles of corrugated or solid fibreboard. They can be used to fill the space between the inner flaps of RSC, to completely cover the bottom or top of a box, or to separate layers of product. Vertically, they can be used to separate products or add stacking strength.

Tubes or shells are scored rectangles, folded and sometimes joined with tape to forum a multi-sided structure open at both ends. When used as sleeves for individual items such as glassware, adjacent shells provide double protection.

Triangular shells are frequently used for stacking strength in the corners of boxes. Rectangular shells that are the same size and depth as the box (minus the thickness of the box) are called liners.

Partitions or dividers provide a separate cell for each item in a box. They are used primarily for glassware and other fragile articles.

Scored and folded inner packing pieces can take many shapes. Included in this group are built-up pads consisting of multiple pieces glued together.

Inner packing pieces are used for cushioning, suspension and separation, and to fill voids. The suspension function holds the product away from the walls of the box to lessen the impact of drops or bumps. Complete filling of voids created by irregularly shaped products adds stacking strength to the box.

Inner packing forms are usually die cut to position and support irregular products from below, or lock them into position from above. Alternatively, forms can be placed on two sides or ends of a product. Some inner packing forms are extensions of the box flaps.

In many cases, the box itself is rather common, but ingenious inner packing makes an irregular product easy to pack and safe to ship.