Apparatus 42 for masking a nut plate, comprising a rigid plastic masking formation 8, a bore (10, figure 8) extending axially through the formation, and a flexible mandrel 12 extending through the bore to project beyond the formation. The masking formation comprises a masking portion 16 at one end of and extending radially outwardly beyond the body portion 14; and a skirt portion 20 extending from a first face 24 of the masking portion. The mandrel has a first portion 26 locating in the bore, and a second portion 28 of a smaller diameter for locating the apparatus during the painting. No supporting formations (32, figure 1) extend between the body portion and a second face 30 of the masking portion. The body portion and/or the masking portion are provided with internal integral reinforcing causing sufficient thickness to prevent breaking of the masking portion during use of the apparatus. Preferably the reinforcing is an extra wall thickness, the body portion is cylindrical, and the masking portion is a disc.
