Jump Rings are simple loops that serve as connecting points for jewelry components like clasps and chains. They come in many shapes, sizes, textures, and materials but from a functional standpoint they only come in two main forms: open and closed.
Closed jump rings are continuous loops that do not have any openings. This usually means that the ring has been soldered shut if the jump ring is made out of a metal like sterling silver, or gold. As a rule of thumb, the jump ring should always be closed if you are using it as an ending for a bracelet or necklace. One important example is that you should never string pearls or beads onto an open jump ring. Thread and beading wire is usually thin and can slip through the gap of an open jump ring with little resistance.
Ideally, all jump rings should be soldered shut to prevent components in your designs from unhooking from each other. In practice, it can be time consuming and expensive to close every jump ring in your creations, but if you select the right size and thickness of open jump ring, it may not be necessary.
To sum everything up…
In general, as long as your jump rings are not directly connected to thin thread, cord, or beading wire, the jump rings can remain open. It is better to solder shut jump rings when possible but, if you are planning on not soldering one or more of the open jump rings in your design, it is essential to use ones that are sufficiently thick for added security.