This is the frisket and poster board shield used in painting "Phaedra's Iris". The frisket is self explanatory if your familiar with airbrushing. The poster board shield is used in controlling the paint spray. It's held against the support (in this case illustration board.) The airbrush is then used to spray along the edge of the shield to control the spray. It was used to produce some of the more subtle variations on the petals.