Although pallets come in all manner of sizes and configurations, all pallets fall into two very broad categories: "stringer" pallets and "block" pallets.
Stringer-class pallets utilize rectangular stringers (or also known as runners)- wood components that run the full length of the pallet. The top deck is fastened to the top edge of the stringers. For Double-face pallets, the bottom deck is fastened to the bottom edge of the stringers.
Block-class pallets utilize rectangular blocks (or also known as cylindrical posts), which separate the top deck from bottom deck (if Double-Face). Block pallets with lumber decks have top stringerboards, which run the full length of the pallet and are fastened to the blocks.