Substitute flag
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Substitute flags are part of the international maritime signal flag set. Their purpose is to allow messages with duplicate characters to be signalled without the need for multiple sets of flags.
The four NATO substitute flags are as follows:
| Image:ICS Repeat One.svg | Image:ICS Repeat Two.svg | Image:ICS Repeat Three.svg | Image:ICS Repeat Four.svg |
| First substitute | Second substitute | Third substitute | Fourth substitute |
To demonstrate their use, here are some messages and the way they would be encoded:

