The overall goal of the 2019 Cornerstone Project is to advance the scale-up of evidence-based services that reduce overdose risk during and upon release from incarceration in jail. The Project examines four evidence-based overdose prevention services in jails serving counties most affected by the opioid overdose crisis. These four services include screening for substance use disorder, overdose education and naloxone distribution, linkage to care upon release, and maintenance medication-assisted treatment (maintenance MAT). The report provides a sections regarding jails and staff, why overdose prevention services are needed in jails, training opportunities, lessons learned, and references.