Magic squares are also the source of the sigils used to invoke various angelic Powers in Ceremonial Magic. The squares were not primarily numeric in nature when they originated: the Hebrew alephbeth, which was used to fill in the various spaces, is both numerical and alphabetic. As numbers in the squares add up no matter which way one counts them, so do the letters that represented them in Hebrew form the same words no matter how they are read. To invoke the Power one wishes, one draws the appropriate Magic square, then "connects the dots (letters)" on that square to spell the name of the Power.
The squares are used in talismanic magic. The squares can be inscribed on jewellry, clothing, parchment, virtually anything. They can be carried with you, or placed on an altar while doing spellwork. If I'm doing something specific, and want a certain planetary influence, I will draw that planets square on parchment, and place it under the candle, or on the altar, etc.