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.
How is piercing performed? For piercing earlobes, a single-use, sterilized piercing gun is typically used to insert an earring into the earlobe. For other parts of the body, a hollow needle is used to pierce a hole in the skin. The person performing the piercing then inserts a piece of jewelry into the hole.