In the level "A Stealthy Approach" when you get to the hook on the right of the
screen there is a small boulder (Note: it is slippery). Jump on to the boulder and
straight ahead there should be a larger boulder covered in ferns kind of blending
in. Jump onto that boulder then doublejump to the left. Then you should either
land on the gate to where you just juump off or you jumped over it.