A guild is an association of artisans or merchants who control the practice of their craft in a particular town. The earliest types of guild were formed as confraternities of tradesmen. They were organized in a manner something between a professional association, trade union, a cartel, and a secret society. They often depended on grants of letters patent by a monarch or other authority to enforce the flow of trade to their self-employed members, and to retain ownership of tools and the supply of materials. A lasting legacy of traditional guilds are the constructed and used as meeting places.