This note summarises practices and lessons learned from the Savings at the Frontier (SatF) programme on providing funding and technical assistance to financial service providers (FSPs). SatF is a $17.6 million partnership between Mastercard Foundation and Oxford Policy Management (OPM). The note outlines how the concept of partnership underpins our approach to adaptive management and the central tool to its implementation: the two-way promise card. We hope that this note will be useful for donors, programme designers, and those working with financial sector stakeholders to find innovative ways of serving the previously underserved. It also offers practical examples of adaptation for fund management and monitoring, evaluation, accountability, and learning specialists.