Rapping-plate
An iron plate inserted in a pattern at such places as it may be desired to effect a jarring or loosening of the same. Ordinarily these plates are sunk down even with the surface, and fastened with common wood screws. For light patterns easy to loosen these answer well enough; but in larger ones it becomes necessary to make the plates strong, with more surface, and secure them by bolts to a similar one on the opposite side of the pattern. By this means the nuts will always bring both plates close to the pattern, and thus obviate the unpleasantness which is sure to follow if the common screw-plates are used. Another advantage the bolted plates offer is that the upper plate may have a threaded hole in which to insert an iron screw for drawing out the pattern. These are often called screw-plates. They are much better than driving spikes into the pattern. See LOOSENING-BAR.