Abstract: A gauge for measuring a change in the spacing between two locations has a support that is fixed at one of the locations and a wheel pivotal on the support about an upright axis and having an outer periphery. The wheel periphery and the support have juxtaposed portions one of which is provided with a pointer and the other of which is provided with a scale so that the pointer moves along the scale as the wheel pivots on the support. A flexible belt has an inner end anchored on the support, a middle portion, and an outer end attached at the other location. This outer end is releasably fixed to the wheel periphery and a spring urges the wheel rotationally on the support in a direction pulling the middle belt portion taut between the locations. Thus as the two locations move relative to each other the pointer moves relative to the scale.