It is one thing to create a security interest with your customer. It is another to have it enforceable against third parties. Most of the ways of perfecting security interests come from the idea of giving notice to third parties that the lien exists. The UCC is specific about how security interests are perfected in certain types of property. If the UCC requires a certain type of perfection, other types will not work.
Some liens require no special steps for perfection.
Some security interests in consumer goods that are in the hands of the consumer are automatically perfected. The security interest you granted in the refrigerator you bought on credit requires no further act to have it perfected. The next simplest form of perfection is perfection by possession. A security interest in almost any type of personal property can be perfected by the secured party actually holding the goods. When a bank takes jewelry as security for a loan, it may actually take the items into its possession and store them.