A Secret Lock for a Cabinet Door THE method of locking shown in the illustrations is suitable for secret doors or panels which are not supposed to open, or it may be used on hinged cupboard or cabinet doors in addition to or in the absence of an ordinary lock. The principle is that of an inside latch or bolt operated by a knife blade, or similar thin instrument, put through a crack between the door and its framework. If a crack for this purpose is undesirable it would be easy with a little ingenuity to work the bolts by a string or wire carried to a convenient point away from the door. Although the method of operating the lock may give the idea that it is an insecure and weak fastening, it actually may be very strong indeed, for the strength of a lock does not depend on the size or character of the key which opens it. Fig. 1.—Panel with swivel cross bar. Fig. 1 shows a panel or cover and the opening into which it fits. A swiveling cross bar is pivoted to the inside face of the panel.. When in the horizontal position the ends of the bar project and fit either behind adjoining panels or into slots, and the panel is locked in place. When the bar is swung into the position shown by the dotted lines its ends are flush with the edges of the panel. Stops are inserted as shown to permit only just the amount of swing required. The lower end of the panel has fixed pins or dowels to secure it, or the wood may be tongued or rebated. Screws with their heads filed off make good pins. Shoulders are necessary in the opening to prevent the panel from being forced inwards, and when it is locked it should be tight. If desirable nail heads may be driven in at each end to give it the appearance of being nailed in place. The cross bar shown in Fig. 2 is a neater shape than the simpler form in Fig. 1. Its ends are cut so that the points are central instead of being at opposite edges of the bar. Besides this it will be seen in the dotted position that the portion cut from the highest part gives a horizontal edge which can be set to just clear the shoulder against which the panel beds and so the center of the bar can be slightly nearer the end of the panel. The way the bar is marked out is apparent at D. It may be of wood or metal. So far the examples show bars running across the panel and securing it on both sides. Fig. 3 shows a hinged door with short fastenings at the side which opens. They are pivoted midway of their length so that they will balance. The dotted vertical pieces which cross them are guides which act both as stops and relieve the central screw from strain if an attempt is made to pry the door open. Unless the panel is very narrow these would be necessary in Figs. 1 and 2. The stops shown in Pig. 1 are suitable where little strength is required but if the panel is forced outward the bar. secured only at Fig. 4.—Wooden guides and wire fastening. the center, may break or bend and the screw be loosened. Combined guides and stops, as shown in Fig. 4, screwed to the door close to the edge, prevent this and greatly strengthen the fastening. The double-ended guide in Fig. 4 stops the bar in each direction and keeps it close to the door surface. The single one is intended for use where there is not room for the longer one. It would be suitable for stopping against the lower edges of the bars in Figs. 1 and 2, at the right-hand sides, where, in the dotted position, there is no room above the bar for attaching a double stop and guide. Fig. 4 also shows a fastening on the same principle made of wire instead of wood. The wire is bent to a curve so that its ends project nearly at right angles in all positions of its travel. If it was straight and consequently at right angles in one position and sloping in the other a knife would not work it so easily. Moreover when bent its extension can be adjusted exactly as required by further bending.
This article was originally published with the title "Suggestions for the Workshop" in Scientific American 105, 23, 497 (December 1911)