I am about to fabricate an exterior French door entrance. My customer is looking for a 3 point locking device. It works like a push bar, but uses a lever to open and lock. The 3 points being the top into the header, in the bottom at the threshold, and the other door which will be locked with flush bolts in the top and bottom. Any direction will be appreciated.
(Architectural Woodworking Forum)
From contributor D:
Paired exterior doors historically had one leaf of the pair retained by a surface mounted Cremone bolt. In some cases both leaves had the Cremone bolts. Von Morris, Baldwin, Whitechapel and others offer versions of this hardware. Often, the other leaf was retained by a rabbet, forgoing the need for a second surface bolt or flush bolts. These types of units were in wide favor, used as windows, since they could be swung open in fair weather for easy access to patios, etc. While this application was widely used in many parts of the world, the French get the credit for it.
The current flavor of multipoint latching includes types where both doors have shoot bolts that are let into the edges and engage the head and the sill, and one leaf of the pair (the active door) has a third bolt that engages the passive door. The active door usually includes a lock cylinder (either American or European type). A search for multipoint latching will yield some results, but the hardware is not available through the normal channels, and there is a learning curve and certain equipment required to utilize the product.
French doors are made in France, and the phrase has been misapplied by American marketers enough to render it meaningless by trying to add cachet to their mundane product. The real thing is available for viewing in the US, notably at the Biltmore House in Asheville, NC.
Of course, those of us that work with wood know what causes and prevents warping and know that the hardware choice will have nothing to do with preventing warping. As for security, most of the alleged "French" doors have glass in them. Code requires a thumb turn cylinder on the inside on the door, so just break a glass unit and turn the latch, and so much for security.