Icons of configured rules

Looking at the symbols of my rules, I see several rules which have the hammer and wrench icon while others don’t.
What is the meaning of this icon and the other icons I see in the Rules and Alerts dialog?

Some actions have a unique symbol to indicate the action that is configured for the rule. For all other actions, the the hammer and wrench icon will be displayed.

	Display the New Item Alert window
	Play a sound
	Move to a specific folder
	Copy to a specific folder
	Mark it as high importance
	Mark it as low importance
	Mark it as normal importance
	Flag message for Follow Up
	Delete it (but not the "permanently delete it action")
	Used for all other actions

Note: For an overview of the used icons for messages, tasks, calendar and other items, see this guide.