Sentence:  [based on information from Major Hill, Master of the Silver Mills, in 1662, descibing silver mining in Cardiganshire] They dig the Oar thus; One holds a little Picque, or Punch of Iron, having a long Handle of Wood which they call a "Gad"; Another with a great Iron Hammer, or <WSD>Sledge</WSD>, drives it into the Vein. 
Meaning of the word marked with <WSD> tags:  A heavy, long handled maul or hammer used to drive stakes, wedges, etc.