I learned a lot of the knots and hitches I use from this site. One of my favorites is the Beer Knot (https://www.animatedknots.com/beer-knot) which I use to make little loops out of paracord. They are one of the few things on the site that are not exactly a hitch or knot but an object that makes tying other knots easier. In my bike repair kit I carry a few in different diameters.

If you wrap it around a pipe or tube using a cow hitch or prusik, it creates an eyelet that is as reliable as if it were welded in place, but is also easily moved by loosening it slightly. On bicycle tours I use them to create ad hoc eyelets on my racks which make lashing oddly-shaped things on the rack easier. They also work great for converting a small diameter eyelet into a larger one.