This question is actually very involved. For a basic understanding, refer to the rekeying manual we have from the consumer dept here. This manual will cover how to pin standard 5 pin cylinders as well as a special compressible cylinder only available in residential locks.
The same basic method is used to re-pin other cylinders (excluding Small Format IC core), but advise the customer to use his/her resources such as a local library or the internet, especially for master keying questions like "How do I master key?"
If the customer is somewhat knowledgeable on keying, you can refer them to the three service manuals we offer on the commercial products
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