"In some cases, you may want to repeat an item and the hierarch­ical branch descended from that item in such a way that a connection is maintained between the structure of the copied branch and the structure of the original branch, with the result that any changes in the original hierarchical structure due to the addition or removal of child items is automatically reflected in the new location. This is especially useful when you borrow a branch from another project’s taxonomy and wish to keep your version of the taxonomy synchro­nized with the original version (see Chapter 13). In OCHRE this form of repetition is called a 'bound branch.'" (Schloen and Schloen 2012, 53)

Bound branches are very useful, especially in the context of building taxonomies. But they can be tricky to keep track of and to use effectively.