This Solutions Guide aims to inform the design and implementation of future interventions that seek to address gaps in sustainable Internet service. It presents a wide body of experience, from Chapter 1 (Identify digitally unconnected (and underserved) geographies), to the many last-mile connectivity case studies shared in Chapter 2 (Review options from the classification of existing solutions). Chapter 3 (Select sustainable solutions by matching viability subject to constraints) highlights how different constraints and considerations will inform what types of intervention may best fit unique situations, and Chapter 4 (Implement interventions to extend sustainable connectivity service) describes various policy and direct interventions that can be leveraged. While the information presented here is not exhaustive – many situations call for hybrid solutions combining technologies and business models – the goal is to begin the process of addressing shortfalls in sustainable, affordable service. The Annexes that follow provide additional resources to support specific interventions. Potential further next steps for engagement include the use of more sophisticated software- supported decision tools, such as those being developed within the overall Last-Mile Connectivity Toolkit programme.