From a start door, go toward the right edge beyond a shop door.
There are two ladders and one is a dummy ladder.
The normal ladder is the left side.
Set a wooden box to under the ladder to climb.
There are total nine wooden boxes on the upper floor.
Make stairs with them and climb up to the upper far left brick floor to get a key.
After got a key, drop six wooden boxes which you used as stairs into the left-side hole.
After you finished to make a pile of boxes, fall down from the left-side edge of the floor.
Then break two wooden boxes beside you to reach a goal door.