The Rules of the Sonar Class are available here to download in PDF format. 
 
To download these pdf files(rather than display them in your browser) right click on the icon and 'Save target as' (or equivalent command) and save to your chosen location. If you are using an Apple Mac, Control-click on the icon and select 'Download Link to disk' and save to your chosen location.

For information on an individual boats measurement certificate please click here for a link to the Sonar Class Association's Measurement Certificate Database