A tool and method of hemming a panel wherein the tool engages a flange to apply a compressive force with a stop initially preventing a distal end of the flange from moving inwardly. The system relates to a method for controlling high intensity discharge lamp comprising supplying a signal of variable frequency and constant filling factor from a switches cascade to a ballast circuit and the lamp, said ballast circuit having at least one condenser and at least one inductance. Thereby, a GaAs semiconductor substrate that allows to obtain a group III-V compound semiconductor device having high properties even when at least one group III-V compound semiconductor layer containing not less than three elements is grown on a main surface, and a method of manufacturing the same are provided. A recess is defined in a sidewall formed on the base at one end of the first channel. The reliability is improved since the value 0 or 1 stored in the data can be accessed through two paths and the operation speed is enhanced since the resistance in the conductive path from the sense amplifier to the ground is effectively reduced when accessing 0. A second conductive film pattern is formed on the first conductive film pattern which is exposed through the second conductive film pattern and a third conductive film is formed on the dielectric film.