A custom unit is a private unit that represents a modified public unit.

When you use the Unit Assistant to modify the composition of a unit that you do not own, Bentley OpenUtilities Designer detects the change, clones the original unit, and adds the custom unit to the database as a private unit. As soon as this new private unit is added to the Units folder, the item is labeled as "Custom" in the Units view and displayed on the Private page of the Units Catalog so you can use it in subsequent designs.

You can select the unit that you want to clone from the list of units displayed in the Units view or from pages of the Units Catalog in the Design Assistant. You can also customize an assigned unit while using the Design Assistant.

If you are a user with the capability to manage public units, make sure you have selected the AutoClone setting on the Unit Assistant's Options menu if you intend to create a custom unit. Otherwise, you will alter the makeup of the original unit. By default, the AutoClone setting is active if you are a user without the capability to edit public units.