Boulder is just that--a boulder. They fall from chutes in Drill Man's stage at regular intervals if Mega Man gets within range. Mega Man can destroy the boulders, which sometimes leave behind power-ups. The chutes themselves cannot be destroyed. Boulders inflict moderate damage, but really become a nuisance once they hit the ground and break into pieces. However, if Mega Man destroys all of these pieces (usually with a charge shot), they can yield multiple power-ups at once, which comes in handy for refilling life / weapon energy. Standing under the chutes with a charged Pharaoh Shot is a safe and easy way to farm pickups.