Boom vang
![On larger sailboats, the boom vang is often a combination of a spring-loaded telescopic tube to support the boom and a pulley system to tighten the vang as shown in this picture.](/Images/godic/202501/01/Boomvang1251.jpg")
![Position du hale-bas](/Images/godic/202501/01/Gréement.svg1251.png")
A boom vang (US) or kicking strap (UK) is a line or piston system on a sailboat used to exert downward force on the boom and thus control the shape of the sail. The Collins English Dictionary defines it as "A rope or tackle extended from the boom of a fore-and-aft mainsail to a deck fitting of a vessel when running, in order to keep the boom from riding up".