Marking your golf ball on the green is an important part of golf etiquette, and the rules of golf require that the position of any ball to be lifted must marked. When your group has reached the green and you're not the first to play, replace your ball with a marker to give other players a clear shot at the hole. After they've putted, replace your ball to make your putt. Magnetic ball markers are one common type of marker -- although the term is something of a misnomer, since the markers themselves typically are not magnetized.
Although a few makers market markers that have actually been magnetized, the majority of golf ball markers sold under the moniker of "magnetic marker," by far, are metal or metal-backed markers that come with a magnetic carrier, often a clip that can go on a golf hat or on a belt for easy access. The markers come in a variety of shapes and surface finishes, commonly displaying a monogram, logo or design. Some of the top-surface finishes on magnetic markers that aren't all metal include cloisonné, thin wood veneer, or even rhinestones.
With a magnetic marker, it snaps firmly onto the magnet in the carrier, and it's always where you expect it to be. Markers that don't come with a magnetic carrier can be difficult to deal with and easy to lose. Some markers of materials such as plastic or wood attach to a golf bag or cart, while others you might keep in your pocket. Depending on what you carry in your pocket, loose markers can require a good deal of fishing and fumbling. It's also easy for a nonmagnetic marker to drop onto the fairway without your knowledge, and although they are inexpensive, it is inconvenient to notice that your marker has gone missing.
Many magnetic ball markers come as part of a set of other useful golf items related to putting, such as a divot tool or a clip of tees. It's common for a magnetic marker to fit into a circular indentation on a divot tool that has a magnet embedded in it. Some manufacturers produce hats that have a magnet buried in the brim; you can stick the marker on the brim and remove it when needed.
When placing your ball marker, always situate it carefully behind your ball and do not lift the ball until the marker is in place. Remove the ball and wipe it off, if needed, while waiting for the other players to putt. When it's your turn to play, replace the ball to the front side of the marker and remove the marker once the ball is stationary.