- stand at entrance to hallway (facing "up" in the diagram) - starting at room corner on your left, angle up and to the right 45 degrees until you reach other side of hallway - starting where you reached other side of hallway, angle down and to the right cutting off a corner of the toy storage/HVAC area - door to HT goes on the first new wall, door to toy storage goes on second new wall - depends on whether the corner of the HVAC/toy storage room you just cut off had anything important in it, like the HVAC