an expansion joint in which by means of movability of expansion shim assemblies in a sustaining pedestal and a stepped bench unit formed of a pair of benches at different elevation disposed beneath the sustaining pedestal so as to withstand vibration of roadway or bridge and instantly rescue the roadway or bridge from collapsing . before construction of the same , a specially designed h configurated clearance gage is used for determining clearances of adjacent component parts of the expansion joint resulting in getting an accurate and effective structure of the expansion joint .