Because I like to work on multiple projects at once, I only store UFOs (things that I have stopped working on for whatever reason) and those get put in clear plastic project boxes made for storing scrapbook paper. I also include any fabric, thread, etc. needed to finish them and sometimes a note about why they are a UFO. They do get finished one way or another- but they might be in Area51 for years before that happens
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As for WIPs- I currently have five. Three are stashed on my design wall, one is on the Sweet Sixteen and another is on the PC420.
Rob