Lashing is a type of knot where you wrap around the object several times to secure it. A granny knot is slang for ‘whatever knot you happen to know, tie a bunch’. Granny knots are often a stack of square knots.
That’s a new one to me, but it does fit the context better than the “traditional” definition of a granny knot, which is a backwards square knot (aka reef knot).
Granny knots come undone when you don’t want them too, and are hard to take apart intentionally (like square knots), so they’re terrible knots.
If your shoelaces come untied, it may be because you tied the loops in a granny knot, instead of a square! (When tied correctly, the loops lie across the foot, not up&down its length.)
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