A ring spanner is also known as a plumb bob, which is one of the most straightforward tools around. It has two round heads on both ends. You place one of the round heads or rings over the head of a bolt or nut. Then, you will use the spanner to push the flat sides of the fastener. With the applied pressure, you can turn the head of the fastener.
One of the advantages of using a ring spanner is that this tool is less likely to slip off the bolt or nut. An open-end spanner has a higher chance of slipping because there is a hole on one side. On the other hand, a ring spanner completely covers the fastener on all sides. Therefore, you can turn the tool in wider arcs without much difficulty. You can then finish your job faster and more efficiently.
A ring spanner has different profiles where the head can have a different number of points and troughs. A bi-hex, for instance, has 12 points, allowing you to lock fasteners in smaller spaces than a 6-point spanner.