Local Board Permissions for SMF 1.1.x
From Online Manual
Local Board Permissions in SMF 1.1.x allow the administrator to set different permissions on different boards.
To enable local permissions, go to Admin > Permissions > Settings > Enable advanced by-board permissions. Next, set the desired board to use local permissions under the "Permissions by board" tab. Click on the board name to add or change the permissions for each group. These permissions will only apply to this one particular board. For each board that requires custom permissions, you would need to choose the board name and choose the local board permissions for each membergroup. For example, once you have added local permissions for a board, you will need to check every membergroup, to make sure that it does not have the required permissions.
Things are handled somewhat differently in SMF 2.0.x. For more information on that, please see All about permission profiles