A bicycle simulation system that can be easily transported includes a frame, a steering handle operated by a rider, a left-right pair of pedals to be operated by the rider for rotating a flywheel, two front forks for supporting the head tube and a rotatable rear wheel. The structure includes a set of extensions for supporting the wafer and a set of extensions supporting the mask. A database manager executing on a device may receive a request to register an application to be notified when a first table of a plurality of tables in a database is changed. A second magnet is disposed on the base component at an intermediate position between the closed position and the opened position. Each open end wrench head is of a different size from the other. The display medium and the sealant are respectively disposed in the display and the sealant region between the first and the second substrate.