The subject quite frequently pops up in discussions (see the Forced deep throat forum thread). The main question is how to mount a dildo and make sure that it will not leave the mouth and throat of the self-bound person, but will allow some back and forth movements (for example, to pull the dildo out of the throat to relax and take a breath).

The attached photo shows how it can be achieved. You ideas on how to simplify this design are very welcome.