Copyright protection extends to your instructions and template drawings for the quilt. Merely seal the originals in an envelope, mail them to yourself and file the unopened contents in the event of future infringement lawsuits. Since the copyright law of 1978 states protection begins immediately upon creating a work, you no longer need to register with The Library of Congress. Well, not quite. Though the symbol appearing on your instructions announces that you claim the design and it is not in the Public Domain, an important reason remains to register your copyright formally.
Registration is a prerequisite to infringement suits.
If someone copies your new booklet of instructions and you never registered it formally, you will have to delay proceedings. You will find limits on the amount you can collect even if you prove the design is yours. Placing the copyright symbol on your pattern instructions is not the same as registering the copyright with the Library of Congress. Since 1978, a work is copyrighted from the moment you put it on paper. It announces your intention to claim the work as yours, preventing it from entering the Public Domain.