A ladder strap is made by joining\u2014for example, by co-molding\u2014a first, relatively supple material, defining a lower strap portion with a second, relatively hard material defining an upper strap portion. The inner cavity tapers transversely outwardly along the longitudinal axis from a mid section to each of the first and second spaced apart opposed ends. A location signal is computed by a processor and transmitted to the GPS receiver. In this embodiment, the circuitry is configured to reduce a drain-source voltage of the first transistor based on the input signal. Thus, the user only needs to rotate the locking knob to lock the support board onto the back board or to unlock the support board from the back board, so that the support board is mounted on and detached from the back board easily and quickly without using tools and saving a considerable amount of time for a user. The address information is represented by a string of at least one piece of sub information represented by the shape of wobbles of at least one of the plurality of frames.