There are two main kinds of pallets: stringer and block pallets. 

Stringer pallets have three longer pieces of wood (a “stringer”) to support the sides and middle of the parallel boards of wood. These are generally 2-way pallets, because a forklift can only pick them up two different ways.  

The parallel pieces of wood for block pallets are supported by blocks of wood on the sides and middles of each edge. Block pallets, more commonly known as 4-way pallets since they are the same orientation no matter which way they are carried, are generally used for heavier shipments, because they provide more support for the platform.