Ever since moving my websites to Sandvox, I've been bedeviled with one little aspect of creating new themes: modifying the plist. Let's start at the beginning: A. Determine which Sandvox design is closest to the look of the site you want to build. My choice is Clean Sheets, FWIW. B. Do you have any custom Designs already based on this design? If no, the navigate to Applications>Sandvox. If yes, skip to C. 1. Right-click or Control-click on the Sandvox icon, which will bring up a list of choices. Select Show Package Contents. 2. Navigate to Contents>Designs 3. Select the .svxDesign file for the design you've chosen (file names are fairly self-explanatory) and duplicate it. 4. Move the duplicated file to username>Library>Application Support>Sandvox. C. Select either the Sandvox design you've just moved (if the answer to B was "no") or a custom design already in this folder (if the answer to B was "yes") and rename it for the new Design you're creating. For my New Media for Designers + Builders site I'm working on, I renamed the file NewMedia.svxDesign. Now, you're ready to modify the Design. 1. Right-click or Control-click on the .svxDesign file, which will bring up a list of choices. Select Show Package Contents. 2. The file you're looking for is Info.plist, but don't just double-click it. If you do, it'll open it up in Property List Editor, where (for reasons I can't fathom) it's almost impossible to save correctly. I've worked with this for many hours on my first two sites, finally stumbling on the right combination of key and mouse strokes completely by accident, and unable to remember precisely what I did. So don't do that. Instead, do this: 3. Open Info.plist with TextEdit. 4. Change the Bundle identifier to "Sandvox." (don't include ... I'm just using those to make clear that "newthemename" is a variable... the name of your new theme (remove all spaces and other extraneous characters.) 5. Change the title to . 6. Save and close. 7. Modify your Design by changing main.css. I've had great luck with CSSeditor, but that app has been bundled into Espresso, which I haven't worked with yet. In any case, it's the main.css file that determines the look and feel of your custom Design.