Measuring a bicycle chain's pitch can be used to identify chain wear and flag the need for a replacement chain and/or cogs and chainrings. Bicycle Chains: Length, Width, What's Best to Buy etc.
An industrial, or scaffold, piercing is made up of two holes that are connected by a single piece of jewelry (usually a long barbell). An industrial piercing is commonly made through the cartilage on the upper ear, with one hole close to the head and the other further down on the outer rim. Two or more industrials on one ear is sometimes referred to as an ear cage.
The theory that 'daith' piercings help ease migraines is based on the idea that it is the same pressure point as that targeted by acupuncturists to relieve chronic headaches. The theory goes that 'daith' piercings relieve migraines, in a similar way to how acupuncture is used to help ease symptoms.