Early in the episode, Chuck asks Ned if he's sure he doesn't want to untie his apron strings, to which he replies that his apron strings are "securely tied in a double figure-eight follow-through knot". This is meant to imply that he is secure in his decision not to wake the dead anymore. However, this knot is unnecessary to tie two ends together, rather it is used to form a loop on a single end, allowing it to be a point of securing to something else.