reservation Briefs provide guidance on preserving, rehabilitating, and restoring historic buildings. These NPS Publications help historic building owners recognize and resolve common problems prior to work. The briefs are especially useful to Historic Preservation Tax Incentives Program applicants because they recommend methods and approaches for rehabilitating historic buildings that are consistent with their historic character.
Or in other words, how to preserve stuff without screwing it up in some way
NPS Technical Preservation Service Briefs