US Patent 9004836 Security fastener

A security fastener, for use with a corresponding key, having a channel in a head of the security fastener for receiving the key, the bottom of the channel being profiled wherein the depth of the channel varies along the length of the channel; a key for use with a security fastener; a combination, or a kit of parts, comprising a security fastener; a method of manufacturing a security fastener; and a method of processing an order for a security fastener.