Preparatory Work:

To avoid paintwork damage, tape off working area over large area at outlet of wire starter (2) with fabric adhesive tape (1)
Cut off required length (A) from cutting wire (A) = Window diagonal x 4
Check whether wire can get caught on rivets or retainers; if necessary, insert guide needles in bonding joint and guide cutting wire past

Fig 1: Cutting Off Required Length (A) From Cutting Wire
Courtesy of BMW OF NORTH AMERICA, INC.