Mackerel

Smoking was banned in all federal prisons in 2004 (except for staff, who can smoke in designated outdoor areas. If movies are to be believed, cigarettes functioned as a form of currency.

Money is disallowed in prison. Indeed it is a violation of BOP rules to give, borrow or sell any item or service to another inmate. This must surely be the most widely violated rule in prison. While I understand the purpose of the rule, it is impossible to function practically without some prison economy, which necessarily involves an exchange of items or services. Where an economy exists, something inevitably will function as a form of currency.

Believe it or not, the new currency is mackerel, that is, fish bait. A can of mackerel can be purchased for $1.20 in the commissary.

I don't know the going rate for very many services but I know the standard rate for a haircut is 2 cans. In addition, some rooms agree to contribute 2 cans per inmate per month to pay someone to clean their room every day (instead of each roommate taking a turn.)

Some inmates literally have no one on the outside to fund their commissary account. And you only make about $17/month working. Therefore, they basically will offer their services in exchange for mackerel, which they can then offer to another inmate to purchase items from the commissary for them.

Most of these kinds of exchanges are harmless at worst and helpful at best. Thus, as long as they are handled discreetly, the COs don't go on witch hunts looking for violations.

While I have not witnessed it, I am told there are more sinister exchanges. The worst being when one inmate extorts goods or services from another with physical threats. I think this is more an issue in higher security prisons than the camps where physical violence is rare.