Unlike braided rope, twisted rope will unravel if the ends are not ‘whipped.’ Whipping is the term for securing the ends of a rope so it will not fray or start to unravel. There are many different techniques for whipping. Some involve using the strands of the rope itself to create a knot at the end of the rope. The thistle knot or wall knot are examples of this. They usually leave a substantial bulge in the rope that can make it difficult to pull the rope through tight openings. There is also a whole family of ways to whip rope using a smaller diameter rope wrapped around the larger rope.
On my hemp rope I use a quick an easy method involving the double constrictor knot. I have a video showing how it is tied on YouTube. This is the link to the double constrictor knot video. It is a little harder to tie with string than larger rope, like I use in the video. Also be sure leave long ends on the rope for tying. It is easier to work with and gives adequate purchase for the final tightening.
I usually just use ordinary string. Once the knot is centered and the loops pulled snug by alternately pulling on each end of the string, both ends can be pulled tight to secure the knot. Scissors can be used to trim the ends off very close the knot itself. The double constrictor knot will not come loose like other knots when the ends are trimmed.
The diameter of the whipped rope is not much larger that the rope. This is very handy when pulling the rope though knots as they are untied. The come right through and the whipping does not get caught.