The most common use for a spanner wrench is the kitchen sink drain. The drain is secured to the underside of the sink by a large-threaded ring. The ring has tabs or grooves on the outside for a reason. The spanner wrench latches onto the tabs or grooves, making it possible to tighten or loosen the ring.
A bathroom sink drain is similar to a kitchen sink but smaller. Spanner wrenches come in different sizes to fit into different-sized rings. You use a smaller spanner wrench to tighten or loosen the bathroom sink drain. It's a pretty low-tech tool, but it does the job of tightening and loosening sink drain rings.
If you look closely at a fire hydrant, notice the large caps have grooves or tabs. A specially designed spanner wrench fits into the cap, allowing for easy removal and replacement. The El Camino Fire Academy in Torrance, California, specifies a spanner wrench as required equipment for a firefighter.
Many automotive components have a large ring or object that has to be tightened or loosened. An oil filter is a very common object that requires a wrench to loosen. A specialized spanner wrench, called an oil filter wrench, has a steel ban that grips the filter. When you pull on the handle, the band tightens, gripping the filter. Other times, shock absorbers may have large adjustment rings to adjust the ride. A spanner wrench reaches all the way around the shock absorber, to tighten or loosen the adjustment ring. .