Hi, Richard,
Here's what you do... in the Data Types section, right-click to create a new data type. Give it a name according to what data it will contain (a checkbox list of sizes, or colors or options or whatever).
Then, in the Rendercontrol field, select "Checkbox List". Click Save.
Now, add prevalues for all the checkbox fields you want to appear for this datatype.
Finally, add your new datatype to your document type.
cheers,
doug.
MVP 2007-2009 - Official Umbraco Trainer for North America -
Percipient Studios