No. The Dek-Block® Pier is designed to accept a wide variety of finished wood sizes distributed throughout the US. Depending on the wood in your area the 4"x4" post may fit loosely into the Dek-Block® pier, this is fine and does not need to be corrected. Once built and everything is secured your deck will be very sturdy. If you want you may place a shim on either side of the 4"x4" post but doing so is not necessary.

If your 4"x4" post seems too large or is not fitting properly you may have to remove some left over debris from the pocket of the Dek-Block® Pier. Occasionally you may have to drive the post in place using force from a hammer.