Symbols and signs are older than written text. In short, it's about this: a shy person is trying to tell something important to an idiot.

From cave paintings to traffic signs, communication through symbols is a proven method with a long history. These can be used to tell important messages such as warnings or guidance towards good things. By carrying patches or badges on your clothes or backpack, you can identify with a group or signal an interest in various things.

Patches and insignia in military use

In a military context, the most common things to tell with patches are your nationality, branch, rank, and last name. Anything more specific cresses a little bit to the territory of morale patches. In the past, the designs worn as "inside-things" among units or squadrons could be very artistic and detailed. They were probably made with care because they couldn't be simply ripped off in the presence of officers, such as various Velcro-backed "suck-meters" and such.

Fighting troops are in a line of work that can lead to serious injury but thankfully there are pieces of equipment and accessories to deal with those. Medical patches are often used to mark the pouches and bags that have helpful contents in these cases and these can also be worn by people who are more qualified to treat injuries. The real worst-case-scenario folks wear their blood type as well.

The right to wear rank insignia, special patches, or medals can involve hard work and sacrifice. You might want to consider carefully if you want to imply having done something you haven't done or being something you are not. Despite symbols only having the power we give to them, some people take these matters seriously.

Varusteleka's morale patches and others

As neckties and high-heel shoes were a long time ago, morale patches are a current example of something with a military background breaking into civilian use. These usually don't involve complex "who can wear what"-rules but we advise at the very least to read the product description to understand what you are buying. From there, just pick what looks cool to you!