The Merriam-Webster Dictionary of English Usage has a take on this that differs slightly from the one commonly found in usage guides: The distinction between hanged and hung is not an especially useful one although a few commentators claim otherwise.
Using Hung in a Sentence When to use hung: Hung is also the past tense of hang.
For sure, inamimate things incl.
The exception comes where hang means to put to death by hanging.
In all other senses of the word, hung is the preferred form as past tense and past participle, as in I hung my child's picture above my desk.
Wells, The Time Machine, Ch.