If you want to enforce a block on everyone at a specific time, follow these simple steps.

1. Configure a closed policy.

2. Schedule the policy so that it effects all users at the specific time.

Hint: If you have just one workstation group but lots of user groups, schedule the policy to the one workstation group at the appropriate times. This will take precedence over whatever policies are configured for users (see "How do I know which policy is in use?").