The thickness of the shackle or links is not the only measure of a lock's security, however. They are vulnerable to all manner of attacks from picking and prying to twisting and freezing. As a result, several bodies award certification to locks they have put through testing. In the UK, where Cyclingnews is based, Sold Secure is recognised as a leading testing and certification service and is affiliated to the Home Office and police service. Although not a definitive guide to a lock's security, it is recognised by many insurance companies and we have therefore used this as our main guide to a lock's effectiveness. Some of the locks included have been given seals of approval from other organisations such as Secured By Design, the SBSC in Sweden, the Dutch ART Foundation and Denmark's Varefakta.