Looked it up:

In England, as well as in the early American years, prisoners left in the stocks or pillory overnight were often raped. The punishment was virtually an invitation to rape, with the prisoner firmly anchored and unable to turn his head to see who was behind him.

The general knowledge of such assaults occurring would suggest that judges were just as aware that they were imposing rape as punishment as were Arab harem keepers who more directly imposed rape as punishment.

In the modern era, prison administrators have often been accused of tolerating, and sometimes deliberately creating, rape situations. In addition to the punishment aspect, prison staff have better control of the population by tacitly consenting to rapes. On the one hand, there is the threat of being placed in a rape vulnerable position, and on the other hand it is a way of keeping the more aggressive prisoners calm and happy, since if they weren't raping they might be rioting. Even in prisons where rapes are rare or nonexistent, there is the constant threat of being transferred to a prison where rape is common--a threat which is sometimes made outright by staff.