Both the structure of rope and the materials it is made of help determine its knot-making properties, allowing you to choose the right rope for your needs. Almost all cordage is built up from threadlike lengths called fibers. How these are twisted or woven together constitutes a rope's structure. The structure can affect the rope's abrasion resistance, stretch, flexibility, handgrip, appearance, and many other qualities.

The material used to make cordage also has a significant effect on the properties of the knots you can tie with it. How expensive a rope is, what it looks like, and how it feels to the touch are all dependent on what type of material it is made of. A useful way to consider the properties of rope materials is to break down cordage into natural and synthetic categories.