Diving Board
A long forward-hanging Arca rail that extends past the forend, giving extra real estate to ride bags and barricades in field matches.
A diving board is an extended length of arca-rail that cantilevers forward off the front of the forend, well past where the handguard ends. The name comes from its silhouette, a flat plank jutting out into open air with nothing under it. Competitors run one so they have more rail to clamp a bipod or tripod head far forward, which lengthens the support base and steadies the rifle.
The real payoff shows up on awkward field positions. With more rail ahead of the muzzle line you can set the rifle deeper onto a shooting-bag or hook it over the lip of a barricade and still find a clamping point, rather than running out of rail right when you need it most. The tradeoff is added weight and length out front, so shooters balance how far the board reaches against how unwieldy the rifle becomes.