In particular, it may limit the construction of piers in the absence of an official pier line (pierhead line).
Various jurisdictions may define it in a different way. A formal definition may read, e.g., as follows: A geographic line along a reach of navigable water that has been adopted by a municipal ordinance and approved by the Department of Natural Resources, and which allows limited filling between this bulkhead line and the original ordinary high water mark, except where such filling is prohibited by the floodway provisions.