Hi there Wanda!
When you have backed up from adjusting the ropes (out of the closeup), use your turn around arrow. When you are facing the other direction, back toward the box, go forward four times. Look down and screen right in front of the ladder leaning against the wall. You will see the outline of the trap door in the floor boards. Click on the outline. You will get a closeup and will be able to open it.
Love, Witchen =O)