This paper presents a cost-effective solution - screwnail indentation for disassembly. It is shown that the screwnail indentation can overcome the geometry uncertainties of used products. A disassembly tool, using the screwnail as the end effector, is introduced. The disassembly task is decomposed into screwnail indentation process, task execution process, and separating process. Based on a kinematically admissible velocity field, an upper-bound analysis is performed for the screwnail indentation process and validated with an experimental set-up. The results can be applied to flexible disassembly.