How can I type special characters? [duplicate]
You need the unicode hex values for these as they aren't part of the standard Compose Key lineup. To work out what the keys were, I copied and pasted the characters off your question and stuck them in this converter. There are many others like it. It gave me the following:
U+25A1 : WHITE SQUARE
U+25A0 : BLACK SQUARE
To enter these, you follow the standard Unicode entry sequence:
Control + Shift + U, unicode hex (in lower case), Return
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