By stuffing the inside of the mouth, you make it impossible for your bottom to move his or her tongue and pronounce words. It's also pretty effective at reducing the volume of his or her screams.
When playing with stuffing-type gags, make sure to agree on a visual safeword and to keep a close eye on your bottom. If the stuffing makes its way into your bottom's airways, you'll want to remove it as fast as possible so your bottom doesn't, you know, die. Safety is your first priority, always!
Tape Gags
Often used in combination with stuffing, tape gags are the ultimate solution if your purpose is to keep your bottom completely silent. Without the ability to move the lips, your bottom can only wimper from his or her throat. Duct tape is a popular choice, but the glue on it can badly damage the skin, so try using masking tape, medical bandages topped over with medical tape, or bondage tape instead.
Tape also restricts breathing, so the safety precautions mentioned above apply here as well. Always make sure that the nose is free of obstructions so your bottom can breathe.
Specialty Gags
Specialty gags refer everything that doesn't quite fit into the above categories. Muzzle and harness gags, corset gags, penis gags, and service gags (gags that include external add-ons like a dildo, a serving tray, a toilet brush, etc...).
These gags are a bit more advanced and have specific aesthetic or practical purposes. They'll fit into one or more of the above categories.
Safety When Using Gags
Using gags can give your scene enhanced erotic power, but it also requires more attention to safety, as your bottom cannot usually clearly express that something is wrong. Agree to a visual safeword (dropping a ball or a bell, tapping the floor or wall, making and releasing a fist several times) and check in on your bottom regularly. Especially when breathing is restricted, panic can set in really quickly, and a panicking human is several times stronger than normal.
When used safely, gags can be a lot of fun! They add a dimension of control and humiliation that appeals to many kinky people. Plus, if you choose the right gag, you can spare your neighbors the humiliation of hearing about what a great time you're having.