you break it with your rubber mallet.
Be the enemy
You find it on the island al the way to the left.After that, you break it with the mallet and pour it on the hot thing to get into the building
he wants to help you break the crab over the hot valve.
You jump on the top of it, and you will get the crab and Sully's key.
It is on game show island but you will have to break the A/C to Get In.
To break the ground you need to jump up where all the switches are and click on them. then you drag them all down and press the green button. Suddenly the ground breaks!
Use the pickax to break out.
the robot drops it on the really hot thing
You have to leave through the roof dome, so you need the mallet from Sully's to break the glass where it is cracked (upper left).
The floor breaks in the water realm to access the underwater ruler.
When you are getting the Living Quarters key from the closet in the Greenhouse of the research lab (production zone), you set off an alarm. Since you cannot leave the way you came, use the rubber mallet to break the glass dome near the upper left corner of the lab.
There is one part of the island where you use it to break glass to make an escape route because the entrance you originally came through you can't get back out of because of a thing that fires water at you. Hope this helped! :)
Some will break, especially near the Balloon Man, but some will just bounce and fall, and not break. You can also push them "off the screen" from Poptropica towers going right. The gargoyles on the skyscraper for Super Power Island will also break if dropped off the building.