Rudimentary Treatise on the Construction of Locks

by A. C. Hobbs; George Dodd

The very first condition to constitute a genuine safe is that it shall have an ample mass of metal—i.e., not of cast-iron, but of wrought-iron, or best of steel, all round it; and especially that the margins of metal all round the door shall be of such huge and surplus scantling that no amount of wedging, by construction possible, should be able to bend any one side sensibly. The next is that the workmanship of every part of the safe be first-class: not that there be merely a moulded door with a showy lock and a trumpery brass-plate upon it, but that every corner and joint of plate with plate in sides and back be effectually united and jointed in the best manner, and that the fitting of the hardened edges of the door shall be like those of a valve, and not even let a watch-spring be got in between. If these obvious conditions be observed, and that the safe itself be properly posited in the premises, it will be found, even with ordinary forms of construction as to doors and bolts, but with a really unpickable lock, a very hard nut for the best burglar to crack.

Chatwood’s Safes.

But much more may be effected without any serious increase of cost. Several forms of safes are now made, the rabbets of the doors of which are so formed that it is almost a physical impossibility to get any wedge, however thin, to drive in between the door and the frame. This is effected in Chatwood’s patent safes (of Bolton and Manchester), as figured above, by making the door rabbets in cross section curvilinear, so that even if the fit be not so perfect but that the edges of a very thin wedge can still be inserted, it yet cannot be driven—for, as it goes forward, it must become curved, and if soft, so as thus to bend, the thin steel will not bear the severe strain of driving, but if hard, it breaks off into short bits close to the entrance. In addition to this Chatwood’s (and we believe other makers’) safes have bolts so constructed, as seen in the figure, that they hook or lock into the bolt recesses in the frame in such a manner as to hold the opposite sides of the frame together, so that, independent of its own proper stiffness, it cannot be bent anywhere, unless by tearing asunder the end on the iron bar constituting each cross-bolt. The bolts, in fact, not only secure the door (as in ordinary) from opening, but secure the door and frame together. With such a safe, if the owner will only provide a proper position for it in his premises, he may rest pretty easy in mind.

Safes are very commonly stood upon a wooden floor, or made to form part of a wood-framed bookcase, or press, or stand in a recess. Often they are comeatable all round, and even underneath, with nought but an inch board below them, and almost always they are left with the front door freely and fully exposed, and with ample and convenient room left all round. This for two or three workmen to manipulate the safe as they may.

Now the only real conditions of safety are that the iron safe should be bedded into brickwork set in Portland cement and sand; or, what is much better, in hard granite or gritstone masonry, bedded in like manner. Without this be done, a fire-proof safe is simply a delusion; constructed how it may be, it is only a crucible of more or less badly-conducting power, in which, after a time longer or shorter, deeds, bank-notes, documents, &c., will be calcined, and coin or jewellery melted, and gems flawed and destroyed. We say this in the full face of the delusive so-called “fiery ordeals” to which many of the so-called double-cased fire-proof safes are alleged to have been for hours exposed. The safe should always be embedded in masonry, and rest upon that in such a way that it cannot get undermined by either fire or burglars.

Whenever the premises admit of it, the door of the safe itself should be set back 10 or 12 inches from the face of the wall in which it is embedded, and an outer door, flush with the face of the wall, should be provided of iron, with a good lock and multiple bolts. The door of the safe should open to the right; and if so, the outer door should open to the left; and neither should open more than square to their position when shut. No one but a practical workman or engineer can have an adequate notion of the extent to which any mechanical operation upon the door of a safe thus circumstanced is hampered by its being set back into the wall, and with an outer door that even when open, cuts off all ready manual access to the inner door from one side.

When premises are constructed, as they should be for all banks and bullion merchants, jewellers, &c., having special regard to a safe as an indisputably secure depository, then the safe should be completely iron or steel cased, and embedded in hard stone masonry (we shall not here go into additional special precautions against the remoter effects of fire), covered in with a strong fire-brick arch, and with nothing but the solid ground below. The door of the safe should only be approachable through an iron or stone-lined passage, just the size of the safe-door, and no more. This should be some feet in length, and have an outer double-cased steel door, or perhaps that and an intermediate iron falling-door or portcullis, between the outer door and the safe-door. With a safe-door so circumstanced, even supposing both these outer doors forced and open, it is almost impracticable for even a single workman, however agile or adroit, to perform any mechanical operation whatever upon the door, least of all upon its surrounding rabbates. These are so close to the solid granite walls, starting out at right angles from the rabbate all round, that he has no room to do anything; and to get a prizing-bar at the door-rabbate, or even to get a second man to assist the first in any way, is impossible, simply for want of room.

The whole of the doors and all the surfaces of such passage should be painted a dull, lustreless black. No one who has not tried it, has any idea of the difficulty of illuminating such a black passage, by even several candles, sufficiently to perform any delicate mechanical operation; and good light is essential to the safe-breaker.

In banks there is no better plan than has been ere now adopted of making the iron safe a great cube, with the door at one side, placing the whole safe with its bottom resting upon the stem or plunger of an hydraulic press, the cylinder of which is fixed in the bottom of the pit in the solid earth, of a size capable of enabling the whole safe to be bodily lowered down into the cavity at the end of the day’s work, and pumped up again out of its hiding-place the next morning. The lever of the hydraulic pump is taken away, and the socket into which it fits is plugged, and the plug locked into its place, and then the pump—situated in a recess in solid masonry—is itself locked up. The top of the safe itself, when it has been lowered to the bottom of its chamber, stands 10 or 12 inches below the floor-level of the stone floor, and a pair of iron doors is then closed over it and locked down.