Past participle and changing endings with auxiliary verb "avere"?
I have read many times that the endings of the past participle doesn't change when used in conjunction with the auxiliary verb "avere". However I am increasingly noticing that is is not the case. For example I recently came across:> Li ho messi in tascaMaybe this *particular* example is wrong or colloquial, I don't know, but I've seen it enough times to make me think this is acceptable. However, I can't find any reference to this in any of my textbooks, nor online. Can anyone help?