of the cutting peripheral edge 66 may vary from a straight line configuration to a serrated configuration as at 66 39 the lifting member or blade 64 may be fixedly connected by appropriate connectors 65 to the leading end or portion of the separating means 52 generally as at 67 therefore it should be apparent that both a concurrently applied forward and separating lifting motion is imparted to the lifting member 59 due to the forward direction of travel of the machine 10 and the reciprocal motion of the separating means 52 to define an operative motion of the lifting member another feature of the present invention is the existence of a mounting structure 69 defining a portion of the frame 12 and disposed in a frontal leading portion theeof the mounting structure 69 is oriented in a somewhat downward angular orientation as clearly shown in fig1 in order to properly place the separating means 52 and more particularly the lifting member 59 and cutting edge 66 thereof in proper separating engagement between the under surface of the covering material and the roof surface 14 the mounting structure includes two spaced apart arms 70 and 72 and a supporting wheel or roller structure 17 the connecting shaft 58 is disposed between arms 70 and 72 and serves as a pivotal axis for the separating.