Porridge
Kiss me's story of WW1 reminded me (not sure why) of a story told to me by a guy called Pete that I worked with at McDonalds back in early 80s. He was a top bloke and nice as pie despite the fact that his other job was burglar. He told us many stories but the one that fits with this topic was about his experiences in Brixton jail.

Aparantly, believe it or not, there is a fair amount of inter-inmate trading going on in our fair prisons. In fact, anything that exists can be traded there though, aside from drugs, the favourite commodities are tobacco and sugar or sweets. The cells that Pete was in were on the landing above the cells with the remand prisoners and the yoof. The accepted way of trading was to dangle the said items out of your cell window in a sugar bag held on a long bit of string, enabling you to swap items with the guy below/above. The normal trade was snout for sugar/sweeties - some of the youngsters still had a sweet tooth and hadn't started smoking yet. The guys upstairs would arrange for the youngsters to put their baccy rations into a dangled sugar bag, it would be reeled up and emptied and then the sweet stuff would be put in, lowered and the yoof could pull it into their cells....only, the bad men upstairs would sometimes put a poo into the sugar bags and dangle them not quite low enough for the lads to easily reach into them. You can picture the disappointment on their poor little faces as they 'lucky dip' for a Mars bar and end up with something not dissimilar in colour, but less appetising - and un-wrapped - in their dirty little mits.
(Che Grimsdale Best before:, Mon 31 Mar 2008, 14:19, 1 reply)

in the States
it is called 'Trafficking and Trading" by the officers (and is illegal) but it is called "fishing" by the inmates. They pull threads out of the sheets to make a rope. Sometimes they might have a stolen paperclip or staple on the end as a hook, sometimes it is just a piece of tape or a knot for weight. The inmates will somehow toss the end of the string (I never saw it from the inmate's view) under their door to another cell. If they are fishing for something, the inmate that is trading with them will toss out a line to catch the 1st line, pull it in, and attach whatever they are trading. They become very adept at this and it is quite a sight to watch all the lines going back and forth across a pod or between the rows.

During lock-downs, the inmates are all fed "johnnies'...which is a sack lunch with a sandwich or two, cereal, and milk. Once the officers have passed out a johnny to each inmate, if there are any left, they will usually put the left-overs either on a table (which only the best at fishing can reach) or on the floor. They then yell out, "if you can fish it, you can have it" and leave the pod. When the officer returns a bit later, they will all be gone.
( flirting with badgers What? It sounded good at the time., Tue 1 Apr 2008, 1:22, closed)