Polished brass finished master keyed single cylinder deadbolt with protect-a-lock feature. It is typically used on a front or back exterior door and is operated with a key from the exterior of the home and a thumbturn from the interior. Use of the home owner key will not lock out the master key Use of the home owner key will permanently lock out the contractor key Ideal for contractor's access to the house during construction period while permitting supervisory or emergency access at all time.