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.
Industrial Metal Supply carries various sizes and thicknesses of aluminum tread plate and steel floor plate. Floor plate, tread plate and diamond plate are all common terms for this material. IMS stocks steel floor plate that meets ASTM A786 standards.