Final answer:
Glass spacers can be used to create the necessary airspace when framing a picture without a mat.
Step-by-step explanation:
If a customer chooses to frame a picture without a mat, glass spacers can be used to create the necessary airspace. Glass spacers are small strips that are placed between the artwork and the frame to keep them from touching. They provide a small gap or airspace that allows for proper air circulation and prevents the artwork from sticking to the glass.