Sentence:  With the tank resting upside down on an old towel or blanket, use a <WSD>spud</WSD> wrench or a large pair of channel-type pliers to loosen the <WSD>spud</WSD> nut. 
Meaning of the word marked with <WSD> tags:  (plumbing) A type of short nut (fastener) threaded on both ends.