Minimum knot form: the Half Knot shows many requirements of many knots, with very few other rope parts contributing nor distracting.  Here we see rope mechanics like many other can b e very direction dependent for how they are applied , to what type of surface shape etc.  Round host is best for most applications, and many fail without a round host.  Round is the Natural, organic answer to a deformity changing direction of the rope path on the host. A corner is a more 'synthetic' wannabe, poor substitute for real round because of the rope architecture and mechanics; just as seen in other materials.
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