About
What is a mainbrace? 
On a First rate Man-o-War, the mainbrace was the largest and heaviest of all the running rigging. It is used to connect the arms to the main mast. The mainbrace on the HMS Victory was 5 inches in diameter!
Enemy gunners commonly aimed for the ship’s rigging during naval battles, with the mainbrace being the prime target. If the mainbrace was shot away, it was usually necessary to repair it during the engagement; the ship was unmanoeuvrable without it and would have to stay on the same tack.
The order “Splice the mainbrace!” was never heard outside the context of battle at sea since repairing it was such a difficult job. The mainbrace ran through blocks, so it could not be repaired with a short splice or a knot. Splicing in a large run of hemp was strenuous work, and generally the ship’s best Able Seamen were chosen to carry out the task under the supervision of the Bosun…usually in a shipyard.
When the order was given at sea, it meant that victory and even continued existence depended on it. On completion of the task, it was customary for the men to be rewarded with an extra ration of rum. The Bosun would take a sip from the ration of each of the men he had selected for task. Eventually the order “Splice the mainbrace” came to mean that the crew would receive an extra ration of rum, and was issued on special occasions: after victory in battle!
Today, “Splice the mainbrace” means to celebrate after a successful battle. It is rarely used anymore due to the phrase fading into history, but when heard it is a welcome sound!
Side note: Admiral Eugene Flucky, when he was the Commanding Officer of the WWII Submarine U.S.S. Barb stored kegs of beer on board, and after every successful battle (and there were many) he would announce to the whole of the crew “SPLICE THE MAINBRACE!” and tap the keg. oogha oogha, dive dive.
