The Passable Platform behavior is an action behavior. When executed, it will cause your selected object (platform) to allow any physics object to pass through the bottom, while keeping the top solid. If you rotate the object by 90º, then the left side of the platform becomes passable.
If you no longer want this effect, simply use another Passable Platform behavior with the "Make Passable" toggle switch off, or use Behavior Off to turn the Passable Platform behavior off.
This behavior will Trigger an event immediately when executed.
This is the object you want to make a passable platform. By default this is the current object selected. You can change this to any other object in your scene.
If this toggle is off, the behavior no longer allows physics objects through the bottom. This removes the passable effect of the behavior.
This outputs the Object ID.
If you want to make a side scroller platformer game, you can make platforms where your main character can jump through the bottom and land on top.