1) Pick a place where you want to set the ladder.
2) Place appoximately 2 inch out from the roof edge, that makes a ladder
      stop collapsing to the side.
3) Hammer 4-6 nails to LASSIS nail hole properly.
4) Inset the round metal bar into the ladder hole.
      (Use lower hole than the roof surface edge, parapet, wall)
       This chain stops the sliding.
5) Lock the chain with round bar(This chain needs to be loose).