Reconfigurable computing is a hot topic for research, as the possibilities and the technology offered by the reconfigurable devices improve year after year both in terms of available configurable logic resources and the possibilities offered to exploit them. This has led CAD tools to grow both in complexity and effectiveness. The expertise required to develop and test a complete system-on-chip using vendors tools has subsequently increased, forcing some designers to create their own tools as support to official development flows. Within this field quite few works have been developed, with respect to the huge effort that has been spent in the exploitation of architectural designs. ReBit is an open-source tool able to help the designer in exploring different placement solutions in the architecture refinement process and in testing the correct execution of an application on a real device.