You've read The Way of the Adamantine Fist by the Dwarven Monk, Greshko Steelbiter. By focusing his ki into his fists he claims to have been able to punch through solid adamantine. You're not sure you could do that, but you can sure punch things really hard.

You gain the following Martial Art:

Sunder: Immediately after you take the Attack action on your turn, you can spend 1 ki point to force your opponent to make a constitution saving through against your martial arts DC. If the creature fails for the next minute they are vulnerable to bludgeoning damage. 

If you use this ability on a structure there is no save, but you deal an additional +10 damage to the target.