splice the main brace
splice the mainbrace
nautical To issue and partake in an extra ration of alcoholic spirits, especially rum or grog, amongst members of crew aboard a sea vessel. (The mainbrace, also spelled "main brace," is a brace attached to the main yard on sailing ships. "Splicing the mainbrace" was originally the very difficult job of repairing this brace, one which earned the repairman an extra ration of spirits; eventually, this euphemistic secondary meaning became the primary one.) As part of the celebrations for her Diamond Jubilee, the Queen gave the order to all in the Royal Navy to splice the mainbrace as a gesture of good cheer.
See also: splice
splice the main brace1 (in the Royal Navy) serve out an extra tot of rum. 2 serve out or start to consume alcoholic drinks. British informal
A sailing ship's main brace is a rope attached to its main spar. Splicing it (making a connection in it by interweaving strands) would have been a particularly onerous task, and the phrase probably arose from the custom of awarding sailors who did it an extra ration of rum.