The BlockBreak Event is fired whenever a block is being placed. You can cancel the event to prevent the block from being placed.

You will need to cast the event in the function header as this class:
crafttweaker.event.BlockPlaceEvent
You can, of course, also import the class before and use that name then.

BlockPlace Events implement the following interfaces and are able to call all of their methods/getters/setters as well:

• IEventCancelable
• IBlockEvent

The following information can be retrieved from the event:

ZenGetter	ZenSetter	Type
ZenGetter player	ZenSetter ​	Type IPlayer
ZenGetter current	ZenSetter ​	Type IBlockState
ZenGetter placedAgainst	ZenSetter ​	Type IBlockState
ZenGetter hand	ZenSetter ​	Type String