Two types of mechanical fasteners are typically used in the fabrication of block-style wood pallets; those that attach pallet parts to blocks (block fasteners) and those that attach pallet deckboards to stringerboards (mat fasteners). The quality of the block fastener used has been shown to affect the diagonal rigidity of pallets, and within certain limits, the more rigid the pallet the more structurally durable. The current study was an attempt to determine the impact of mat fastener stiffness on the rigidity of block-style pallets. It was determined from corner drop tests that the difference in stiffness between certain regular-stock steel clinched nails and staples, typically used as mat fasteners in most block pallets, has no effect on the diagonal rigidity. The rigidity of most block style pallets manufactured today seems to be determined exclusively by the quality of the block fastener. However, block pallets made of dense hardwoods with very stiff helically threaded hardened steel nails for mat assembly averaged 31 percent more rigid than those made with regular-stock steel nails or staples. The performance of block-style pallets made with dense hardwoods and stringerboards 3/4 inch thick or more can be improved by using quality helically threaded hardened steel nail without clinching.