From the Super Mario Wiki
A Ledge Hammer is an obstacle found in the game Super Mario Galaxy 2. They resemble giant black and orange hammers. They only appear in the Clockwork Ruins Galaxy during the "The Ledge Hammer Trap" mission. A total of six appear during the mission and block the player's path to the star. The main attack of the hammer is crushing Mario or Luigi under its enormous weight. Ledge Hammers also move very quickly, making them a hard to evade obstacle. Luckily, the hammers can be slowed down via the time switch nearby.
 Names in Other Languages