Continuity editing allows film clips to run longer, giving audiences a fuller understanding of scenes by keeping footage continuous without breaks. Montage editing cuts together short clips to show different aspects of a film quickly, allowing viewers to identify elements in a short time. This technique is commonly used in trailers. Establishing shots use long or extreme long shots to establish settings, locations, and characters. Shot reverse shot edits between two shots, showing one character's perspective then the other's in that scene. The 180-degree rule states that successive shots should not cross 180 degrees to keep the line of vision natural. The 30-degree rule ensures successive angles do not exceed 30 degrees to maintain space between characters.