Seals are an important part of both orthodox religious Daoism and folk Daoism and several hundred are in use.
Seals or Fa Yin are typically made of peach wood though some that are geared towards Buddhist deities will be made of sandalwood and carved . The most expensive are made of wood that has been struck by lightning.
Seals are typically consecrated and cultivated over a minimum of forty nine days and aren't just used 'fresh out the box'.
Most people with even a familiar glance at Chinese religious, spiritual and magical practices will be aware that seals are often used to stamp and authorise a talisman once it is complete. It is rather like the way a worker stamps a contract or document with the company seal to show it bears the approved authority of the executive powers of said corporation.
Less well known is that some seals are a magical instrument by themselves which can be worn or carried , to call spirits and interact magically with other beings or natural phenomena. The above is commonly worn by magicians of Maoshan and represents the Liu Ding and Liu Jia Generals who can perform various magical functions.