Modern Magic: A Practical Treatise on the Art of Conjuring

As this “bayonet-catch” is of constant use in magical apparatus, it will be desirable to describe it somewhat minutely. A rectangular cut or slit (see the enlarged view in Fig. 184) is made in the lower edge of the cover b. Its perpendicular arm is about a quarter of an inch in length, and its width about an eighth of an inch. A small pin or stud, about an eighth of an inch in length, projects perpendicularly from the lower edge of c, at such a height that when b is placed over c, the upper or horizontal arm of the slit shall be just level with it. If the upright arm of the slit be brought immediately over this pin, the latter will, as the cover sinks down, travel upward along the opening as far as the junction with the transverse portion of the slit. If the cover be now again lifted, the pin will, of course, offer no obstruction to its removal; but if the cover be first slightly turned to the right, the pin will become engaged in the transverse portion of the slit, and upon then lifting the cover, it will carry with it the pin, and all connected with it. When it is desired to lift off the cover alone, it will only be necessary to turn the cover a little to the left, thus bringing the pin again over the upright portion of the slit.