This is what I have always understood to be the norm; All points of penetration less than 2 inches (50.8mm) from any edge of a stud, joist, plate etc., a striker plate is required to provide protection at the area of support and within 5 inches (127mm) of each side (if appropriate) of the support. At points of penetration 2 to 3 inches (50.8 to 76.2mm) from any edge of a stud, joist, plate, etc., a striker plate is required to provide protection throughout the area of support. At points of penetration greater than 3 inches (76.2mm) from any edge of a stud, joist, plate etc., no protection is required. Tubing routed horizontally through studs shall be protected from puncture threats between the studs using shielding devices provided.