Where the board meets the wave
The rail is a major contact point between board and water. During a turn, the surfer places part of the rail into the wave face to create hold and change direction.
Fuller rails
More volume in the rail can add forgiveness and help the board carry speed. It can also make the rail harder to sink deeply for a lighter surfer or in a tight turn.
Refined rails
Thinner or more tapered rails can engage with less pressure and provide a precise feel. They may be less forgiving when weight is placed poorly or the take-off is unstable.
The rail changes along the board
Nose rails, centre rails and tail rails perform different jobs. A useful assessment looks at the complete rail profile and how it works with rocker, tail and volume distribution.