Rather than pull his own weight, Manfred swung the lead all day - he was too lazy to pull his own weight.
This expression is of a nautical nature. The Leadsman, who was assigned to assess the depth of water under a ship, sat in the chains (i.e. near the mast shrouds) and swung a lead-weighted depth gauge so that it entered the sea near the bows. If he was lazy he just swung the lead without going to the trouble of sounding the depth - calling out an imaginary reading to the Officer of the Watch.