When Custom Actions are used in an AppLife Update project, their properties are persisted into the project file when the project file is saved. When a project is reopened, Make Update must be able to load the assemblies that contain the custom actions that are in the project. If Make Update cannot find a custom action assembly, a placeholder is inserted into the project that maintains the integrity of the custom action property information. You can then locate the appropriate custom action assembly manually. After the assembly is found and loaded, the placeholders are automatically replaced with the appropriate custom action.