26. First, I located where I wanted to drill the corresponding ¾-inch holes for the bulkhead fittings. This was easy as a previous owner already drilled two holes to pass through speaker wire. Next, I drilled and tapped a hole just above the larger one in the A-pillar. This will allow me to use a ¼-20 button head fastener to hold the bulkhead fitting in place since I can’t access the backside of the A-pillar to install the provided collar.