The MoonBoard is a 40-degree-overhanging training board with a fixed grid of standard holds, designed by British climber Ben Moon in 2005. The same board is built worldwide to the same specifications — same wood grain, same hold positions, same hold model. This standardisation means a V8 set on the MoonBoard in Sheffield is the same V8 climbed on the MoonBoard in Boulder. LEDs (or a smartphone app) light up the holds for any of thousands of community-set problems.
MoonBoards are popular in dedicated training spaces and home gyms because they allow direct comparison: climbers know exactly how strong they are relative to the global community. The 40-degree angle places enormous load on the fingers and core, so the board is most useful for intermediate climbers (V4+) building bouldering-specific strength. Beginners typically find every problem too hard.
MoonBoard is one of three major standardised training boards alongside the Kilter Board (variable angle, more dynamic moves) and the Tension Board (smaller, more crimp-focused). Each has a different character. Choosing one comes down to personal preference and which boards are available locally — most serious bouldering gyms now have at least one of the three.