The walkthrough says this (while in the workshop by the pond, at the worktable):
Block and tackle: Turn around to the door. Take the winch-block and tackle (now that we have seen the standing stones around the farmstead and the tilted picture of the standing stone in Rhiannon's bedroom) from the rafter above the door.
Have you also seen the standing stones around the farmstead and also the tilted picture of the standing stone in Rhiannon's bedroom?