A method of joining or repairing metal surface structures. The fixing mechanism includes a fixing member and a screw. Each strut having angularly offset parallel engagement ends which engage with spaced co-parallel drive disks affording a unique rotational linear travel path that allows each of the struts to sequentially engage the ground and propel the assembly forward in a progressive walking like motion when used in combination with corresponding second strut drive assembly. The output of each samplehold circuit is coupled to one input of a multiplexer. The method includes: wirelessly polling the identifier by a roadside radio beacon as a current identifier, generating a parking fee transaction for the identifier if the current identifier is identical to a stored old identifier, storing the current identifier as the old identifier, waiting a predetermined time period, and repeating these steps.