In case you haven't seen one, a chastity belt is a metal belt that fits tightly around the waist, much like a corset. A front plate is attached to the chastity belt so the genitals are not accessible. There is generally a way to allow urine to escape without giving access. The purpose is to render the genitals inaccessible.
During the late 1800's (the Naughty Nineties), there was an unprecedented interest in all things sexual. Museums acquired chastity belts spanning the Crusades through modern times. This interest persisted well into the twentieth century. Without exception all devices exhibited were for female containment. Most were made of iron and either locked or welded on.
In the 1920's a researcher discovered a chastity belt in Florence Italy that dated to the renaissance. Further research unearthed the fact that all the so-called Crusades chastity belts were fakes created in the 1890's. Museums around the world scurried to remove the fakes from display. Since then, the chastity belt remains a footnote on history and it is difficult to find any on display.
The period from 1850 to 1930 is full of truly strange sexual history. For example, in the 1850's it became a widely held belief that male masturbation caused insanity. This triggered nearly a hundred years of increasingly demonic inventions designed to prevent young men from playing with themselves or having wet dreams. Male inmates in asylums were routinely fitted with devices to prevent them from making their conditions worse through ejaculation.
In a nutshell this is the pedigree from which the present chastity play derives. Note that the original purpose of these devices were very different for males and females. Females were protected from penetration by anyone other than their husbands. Males were protected from themselves; prevented from touching and stimulating themselves. Ideally, they were also prevented from nocturnal emissions as well.
Historically, women have been trusted to limit sex to their partners. The Florence chastity belts, and subsequent models, were primarily for the benefit of jealous, possessive husbands. Female orgasms were never the issue. It would be several hundred years before anyone gave them much serious thought.
The significant issue is that male chastity belts are intended to change behavior; the wearer is deprived of the ability to masturbate at will. Given the fact that females can easily learn to orgasm with non-genital contact, a chastity belt is at best a temporary stop to masturbation. It does prevent penetration, but that's about all.
This sets the stage for current play. Interestingly, most of the players do not identify themselves with dominance and submission. They see using the devices as ways to give their fidelity to one another. We'll explore what that means later. According to Paul of Access Denied, chastity belt maker, seventy-five percent of chastity belts are for a male wearer. A substantial portion of female wearers buy the belts for themselves out of concern about rape or other sexual attack. This means that in the main, chastity play is directed at male wearers.