What does a Blue square with a White background mean Code flags have been a long naval tradition and are an excellent method of communication when radios are down or language barriers apply. But they are only effective if you know what they mean. Having a quick reference in the cockpit or at the nav station can help dispel any confusion and keep you and your boat out of danger. This self-adhesive decal provides a guide to alphabet and numeric code flags and their alternate meanings. By having a West Marine code flag decal close by, you will know quickly to steer clear because that Blue square means the vessel in front of you is full speed astern”. Key Features International Alphabet and numeric code flag reference Self-adhesive decal that can be applied in the cockpit or at the nav station Provides visual reference to letter flags and alternative meaning Ideal for cruisers traveling domestically or in international waters