Rullepølse
It is often use on "rugbrød" to make the traditional Danish open-faced sandwich , "smørrebrød" , usually garnished with a thick slice of "sky" and rings of raw onion . 
<triplet> rugbrød <subj> smørrebrød <obj> part of <triplet> smørrebrød <subj> rugbrød <obj> has part <subj> open-faced sandwich <obj> subclass of