BYOB often appears at the bottom of invitations to private parties, most often from poor, impoverished hosts and every time you are invited to a student party. It means bring you own bottle/s, with bottles being easily translated as cans if that is how you like your beer. The idea is to bring something that you yourself would drink1 so that you won't complain to the host that there is nothing there for you to drink. After all you had been warned.
The Inverse Law of BYOB
This law states that no matter how much of your favourite tipple you bring it will be consumed before you have had a sufficient quantity to feel a part of the party. The result is that you end up drinking other people's tipples so that they too suffer from the same dilemma. As a result by two in the morning when the party is in full swing a bottle of malt vinegar is produced and consumed by the party goers, only to be heralded by the cry 'I'm never buying that again'.
The No Hiding Law of BYOB
Some devilish people and especially the host/s may try to conceal their favourite, and usually most expensive, drink somewhere secret. However once the Inverse Law comes into effect the hardened party goer will search out concealed supplies. This may happen accidentally by spotting the host taking a quick swig from a hidden bottle or deliberately searching through possible hiding places. Often, if discovered accidentally, the 'spotter' will promise the 'concealer' never to reveal the location of the stash to anyone so long as they can have just one drink. Do not trust the 'spotter' - within two minutes the remainder of the hidden stash will have been consumed by the whole of the party.