A German wasp (Vespula germanica) . This female was collecting wood pulp on one of the garden fences. Moving backwards the top layer of the wood is gnawed off using the jaws. The collected material is rolled into a ball between the forelegs and the thorax for transportation.
The stripes visible on the planks are spots where material has been collected before. Other wasp species also collect wood from the fences, like this female Symmorphus crassicornis.
References1 Nederlands Soortenregister