Symbols trace a unique visual/tactile path that will establish a relation to a perceptional meaning. A letter could be linked to an utterence of a vowel, or a digit to a numerical base constant. Often it is the combination of symbols that will create a complete picture. However by combining symbols into words they somehow become a new symbol. Sentences are not read letter by letter but word by word. And small mistakes can be skipped over, sometimes you don't even notice them. Even sentences can become a symbol if read often enough. And so even larger structures then sentences can form a complete symbol. Stories are ultimately not formed by sentences, words, letters, or symbols; but the journey in the mind that they will make you take by reading them. Sigils have combined the power of a single symbol with that of a complete story, like a layline for the mind.
A sigil can help its user to fall back into a certain mind-path with just one symbol. An effective tool because sometimes we forget how our thoughts were arranged and would like to recollect that style of thought. This could also be triggered by certain tunes or smells. In that effect a song could also be called a symbol and the same goes for a fragrance.
However with the advent of computers and higher education more people see the world digitally or mathematically. Our world is slowly moving away from natural/chaotic curvy lines to measureable straight lines. Instead of fighting this order a sigilist could embrace it, and many people do without even knowing it. It is hard to remember your PIN code, but nobody has problems with the android pattern unlock. A 3x3 grid with 389112 distinct patterns. Not enough for every person that uses it, so many people share the same unlock-sigil without knowing it. Perhaps you felt stronger about a certain pattern than another, you should consider why that happens.
You could also form your own meaningful sigil this way, with the added benefit of reminding yourself something important everytime you unlock your phone. This site has a very easy generator that makes a 3x3 grid sigil from a sentence. Remember not to sigilize negative thoughts or behaviours, e.g. don't stop something negative, but do something positive.
Another new grid sigil based application, albeit triangular instead of squares, is Meshtag. An interesting alternative to QR codes, although I highly doubt it will be in wide usage.
Magic squares have a lot in common with grid sigils, you could trace a line in the numerical order within the square to form a magical sigil. These are extremely powerful and balanced, and many houses of old used them to empower their family.
Grid sigils are slowly becoming quite popular on computers because they are easy to distinguish and implement. Their power is however limited due to their extreme order-like behaviour and they should be used for two sentence stories at max.