barrier
Objects whose purpose is to form a screen or shield between one area and another.
Barriers are usages assigned to objects whose purpose is to protect or shield one area from forces, things, phenomena, persons, animals, agents, or substances on the other side, or to block or filter information from passing from one side to another. Barriers can have a unidirectional or bidirectional purpose: that is, their intended effect can be to block something coming from one or both sides.
The barrier separates the two sides with respect to a particular influence or passage. Its purpose can concern physical movement, environmental effects, or transmission of information.
The intended effect can operate in one direction or both. A barrier therefore does not have to block every kind of movement or influence equally from each side.