Another variation of lug nut is the "locking wheel nut", which is used as a theft prevention method to keep thieves from stealing a vehicle's wheels. When utilizing locking wheel nuts, one standard lug nut on each wheel is replaced with a nut that requires a unique key (typically a computer-designed, rounded star shape) to fit and remove the nut. This ensures that at least one lug nut will remain attached and, in theory, should prevent theft. However, universal removal tools are available which grip the head of the locking nut using a hardened left-hand thread. The success of locking wheel nuts depends on the determination of the would-be thief and the tools that they have available to them.