Strength parameters for fasteners determined in accordance with the methods prescribed for the European CE-marking leads quite different values for seemingly similar products from different manufactures. The results are hardly repeatable, to some extent due to difficulties in selecting representative timber samples for the testing. Beside this uncertainty, the declared values concerns only structural timber, so no values are available for e.g, LVL or plywood.

This paper gives:

• Examples of the variability of declared strength parameters for ring shank nails for almost similar products.
• Results from withdrawal test for similar nails inserted in the same timber specimens (structural timber and LVL), which is used for investigating similarities and differences between nails and wood.
• Discussion of statistical methods to compare the strength parameters of two nails.
• A proposal for a method that enables to determine accurate strength parameters needed for structural design from comparative tests involving reference fasteners.