This is a basic Tell-Tale crack monitoring gauge that monitors both horizontal and vertical movement across a crack on a flat service to an accuracy of +/- 1.0mm and by interpolation to +/-0.5mm. They are precision gauges that consist of two plates which overlap for a part of their length. The bottom plate is calibrated in milli-metres and the top plate is transparent and marked with a hairline cursor in the form of a cross.
Each Tell-Tale is supplied with a record marking sheet allowing easy comparisons to be made.
They can also be fixed with Araldite.