Border blocks are unbreakable blocks that
prohibit movement through, over or under them.
They are obtained by selecting from the inventory when in creative mode or typing the following command into the chat:
No tool or explosion can damage them.
Students can individually override the border block if the world allows them to enter world builder mode. They can do this by typing the following command into the chat:
The border does not prevent items which can be thrown, such as arrows or tridents, from passing through. Throwing an ender pearl from one platform to another will teleport a student.