A rope gag is a gag for the mouth constructed out of rope, generally as part of a rope bondage scene. As with all gags, it may prevent speaking or fill the mouth thoroughly or increase drooling by holding the mouth open.
More About Rope Gag
An effective rope gag can be achieved any time rope is run through the mouth. A rope gag is sometimes done in conjunction with a rope blindfold or as a way to use up the rope after completing another tie.
Specific rope gag ties also exist that mimic other typical gags such as a bit gag or ball gag by using patterns of rope work or knotwork.
If the rope is used in the mouth, it should be dedicated to that person only, or it should be a synthetic or cotton rope that can be thoroughly washed and sanitized.