I warned a fellow about the Exacto #11 back in the early 70s. He reported back a few weeks later that he had slipped while cutting the abs plastic on a Lanier Transit. The blade went to the hilt in the fleshy base of his thumb on the other hand. He said that it felt like it was stuck when he tried to pull it out so he unscrewed the ferrule on the handle and pulled it off of the blade. He then drove to the local hospital with the blade still embedded where they pulled it out and gave him a tetnus shot.
His comment was "they really are sharp".