Interaction with Objects
Often a player tells the GM that his or her character is doing something and the GM simply describes what, if anything, happens. For example, a character might decide to pull a lever, which might, in turn, raise a portcullis, cause a room to flood with water, or open a secret door in a nearby wall. (87)
Is an ability check necessary? Sometimes interacting with an object will require a successful ability check. For example, in the prior example, if the lever that the character decides to pull is rusted in position, the GM might call for a Strength check to see whether the character can wrench the lever into place. The GM sets the Difficulty Class (DC) for any such check based on the difficulty of the task. (87)
Is an action necessary? During combat, you can interact with one object or feature of the environment for free, during either your move or your action.
However, you use the Use an Object action when the interaction needs special care or presents an unusual obstacle, or if you want to interact with a second object, or when an object requires your action for its use. (91, 94) Some magic items and other special objects require an action to use, as stated in their descriptions. (91)