Instructions
Enter the mouse holes in the northern wall of the Wardrobe Room.
Jump on to the fork handle sticking out of the wall. This will launch you high into the air. Grab the ledge immediately next to the fork to climb up.
Walk east down the path and through the corridor. Following the path you will eventually come to a ledge.
Drop down off the ledge and exit through the mouse hole to get back into the Wardrobe Room. The mouse hole is behind the second fork in the wall and appears as an exit on your map.
Run across the ruler and jump to the other shelf to pick up the Pink Thread.