Find Block Regions in Drupal 7
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In Drupal 7, click on "Structure" and then "Blocks".
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Click on the "Demonstrate block region" link at the top of the page. You'll then see all the block regions for the theme that is enabled for your site.
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Find Block Regions in Drupal 6
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In Drupal 6, go to Administer, then Site building, then Blocks.
Drupal will automatically show you all the block regions for the theme that is enabled on your site.
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