If you want to take it up a notch. When I play dom I like to first put the ball gag & lock it in place. Check to make sure the ball in lodged tightly in the mouth. Then add as many pieces of duct tape you want. Its best when you play a rape victim because you can scream all you want & no one is gonna hear. Gags are the best part!
Just remember that if you use duct tape, you're getting into breathe control territory. The dom has to be very careful to make sure the sub can breathe through the nose. And don't ever leave a sub alone who has been tied up and gagged with tape. Helpless and unable to call for help is a recipe for a visit to the morgue.
bb- When you give advice like this, it would be wise to include the down side of this action. There are many less experienced folks who might take you at your word.... well not to many, I hope.