Re: attaching copper flashing to brick wall
The old-time roofers would brake the counterflashing with a 3/8" flat top and insert that into a raked-out mortar joint, and wedge the c/f in place with strips of scrap metal rolled into a cylinder and flattened, then driven in to the joint to wedge the flashing; the joint could then be mudded in, or sealed with Lexel/Geocel type polyurethane sealant. No exposed fasteners are acceptable, each one is compromising the integrity of the couterflashing. Let's assume for now that there is also the step flashing in place, until we learn otherwise.
Remove not the ancient landmark, which your fathers have set.