Each event in the regatta takes the form of a knockout competition, with each race consisting of two crews racing side by side up the Henley course. The course is marked out by two lines of booms (wooden bars which float on the water, secured between vertical poles), which are placed along the river to form a straight course 2,112 metres long. The course is wide enough to allow two crews to race down with a few metres between them. As such it is not uncommon for inexperienced steersmen or coxswains to crash into the booms, possibly costing their crew the race.