A lemon fork is a fork which is designed for the purpose of serving wedges of lemon at the table. Lemon forks are most commonly set out at formal tea parties, when many guests like to add lemon slices or wedges to their tea, and they can also be brought out on iced tea trays. This particular piece of silverware is a bit esoteric, as it is designed for a single and very specific use, and it can sometimes be difficult to track down as a result. Companies which stock fine silverware typically carry lemon forks, or are able to order them, and you can also find antique versions for sale upon occasion as well.
There are all sorts of examples of esoteric single-purpose silverware which most people are unlikely to encounter outside of very formal situations, and a lemon fork is one such item. Many people wouldn't know what to do with a lemon fork if they saw one; if you learn to identify a lemon fork and use it properly, it's a useful skill, in the event that you attend a formal tea or party. Once you master the lemon fork, the ice cream fork, jelly server, and orange spoon are only a few steps away.
A classic lemon fork is quite small, typically less than the length of a hand. The fork has three tines: a straight central tine, and two splayed side tines. Viewed from above, a lemon fork looks like the victim of a tragic traffic accident, with its side tines curved off in seemingly random directions. However, the design is ideal for wedging the fork into a piece of lemon and gently picking it up.
When a lemon fork is not available, it is also permissible to use tongs to handle lemon slices. Ideally people should not use their hands, both for reasons of common etiquette and to reduce the risk of contamination from dirty hands. Because of the potential for reaction, it is a good idea to serve lemon wedges in china, not in silver, as the acid from the lemon can tarnish the silver, and if you are using a silver lemon fork, you should wash it promptly so that the lemon juice does not linger on it.
You may want to avoid running your lemon fork through the dishwasher, as the tines can be distorted or damaged in the wash. As a general rule, when hand washing fine silverware, whether it is made from silver, stainless, or other materials, you should wash it and dry it immediately afterwards, to prevent spotting or staining. In the case of silver flatware, you may want to set a date every year to polish all of your silver.