The term "fender skirts" in the third instruction at the link above (48-51/52 Truck Shop Manual) is referring to the inner fenders.

gmguy,

AD usually refers to Advance-Design (Chevrolet's name of the 1947-1955 series of Chevrolet trucks). "New Design" (ND is the name the GMC used for 1947-1955 trucks,

The major disassembly differences between most A-D Chevrolet trucks and most ND GMC trucks (the 1947-1953 models) are the way the grills attach and the locations of the parking lamps.