Bondage hoods are most notably used in BDSM, their function being to objectify the wearer as well as providing sensory deprivation, and thus reduce them to the status of a sexual toy, rather than a sexual partner, as part of a scene. A rigid, tight-fitting hood (which typically means leather or latex) greatly reduces a gagged person's ability to make any noise at all. Ponygirl bondage hoods are often an essential fetish garment for BDSM ponyplay. Hoods are also used in head bondage.
A hood can also serve the function of disguising someone's identity when desired, for example at play parties. Tight-fitting open-faced bondage hoods are sometimes worn by dominatrices to depersonalize and erotically objectify the wearer, projecting an image of intimidating sexual power and superiority. Some feel that the aesthetic appeal of these open-faced hoods in BDSM lies in the way that they define the shape of the wearer's head with a smooth, shiny, luxuriant form-fitting fabric and emphasize the dominating woman's stern and haughty expression by elegantly framing her face.
There are many kinds of bondage hoods. A full-face hood is designed to cover the head completely in the manner of a medieval executioner's mask, and thus has an opening at the back to extend the neck hole. This opening may be closed up with a zip or cord. (Spandex hoods are often stretchy enough to go on without any extension of the neck hole.) Other optional openings include two eye holes (sometimes these can be closed using zips), nostril openings, and a mouth opening (which is often closed with a zip or used by a gag that goes over the hood).
Spandex hoods are see-through, so a blindfold is also required if the intention is to keep the person from seeing. Darlex lets very little light through, and the other materials allow virtually no light through at all (though some may get in through breathing holes for the mouth and nostrils and/or poor eye zips).
Hoods can also be complemented by a gag or a mouth dildo, mouth or nostril tubes channeling respiration or even a funnel and tube system allowing forced drinking of any liquid poured in the funnel, such as poop (compare Funnel gag).
Wearing a hood is potentially extremely dangerous, as blocking all access to air will result in rapid asphyxiation. The safety warnings regarding gags also apply. It is wise to use a hood with a mouth hole and a gag over the hood that can be removed quickly.
There are also similar tight-fitting open-faced hoods, which are much safer to use because they do not obstruct the wearer's breathing. One of the most popular kinds is the "ponygirl" hood. This covers the wearer's entire head and neck with a large opening in front that frames the face in the manner of a medieval wimple or traditional nun's habit.
The open-faced hood, which fits snugly over the head much like a swimming cap, sometimes tapers down at the center of the wearer's forehead in a curved V-shape, thus creating a kind of heart-shaped frame for the face.
These hoods may have a small opening at the top, allowing lengthy strands of the wearer's hair to be tightly gathered, threaded through and left hanging down the back of the head as a ponytail, possibly for use in hair bondage. Other hoods of this type have no such opening for hair and instead feature a plume made of artificial hair protruding from the top and down the back of the head as a kind of decorative mock-ponytail. Using these for hair bondage may result in the ponytail breaking off.