While there are, no doubt, other ways to accomplish this magnificent feat with other woodworking tools, I am going to confine my remarks to the use of the Keller Model 2401 Pro Series Dovetail Jig. Keller has other dovetail jig models available but this one seems best to me when considering both function and cost.
This will not be a long article because the operation of this large dovetail jig is elegantly simple, especially when compared to competitive woodworking tools. The complete Keller Dovetail Jig kit consists of two, large aluminum templates, one for the pins and the other for the tails. It also includes two router bits, one for the pins and the other for the tails. These bits have ball bearing tracking collars mounted between the cutter and the bit shaft. The collar tracks around the dovetail template while the bit is cutting into the end grain of the workpiece.
Each template is screwed onto a piece of wood at right angle to the template. This wood is clamped to the one side of the workpiece while the dovetail or pin template rests on the end grain. The only adjustments relate to proper left/right placement of the template along the edge of the workpiece and setting the depth of cut on the router.
Complete instructions come with the Keller Dovetail Jig kit and an instructional video is also available from Keller and its distributors. The width of each dovetail jig template is 24 (a 16 model is available) but the length of cut is not limited to those dimensions. You simply cut all the dovetails on the template and then re-align the template so that the first position on the template is now lined up with the last dovetail (or pin) cut during the initial pass. Theoretically, you could cut dovetails all the way to the moon although no one has tried this yet.
You can save some money by ordering the 16 model but you will have to re-align the dovetail and pin templates more often for wide workpieces. With the standard (larger) dovetail and straight bits that are included, you may cut dovetails in panels that are from 5/8 to 1 thick. A smaller dovetail bit set is available (at extra cost). With the smaller dovetail bits, you may cut dovetails into 3/8 to ¾ material. Normal pin spacing is 1¾ center to center. The dovetail angle is 7 degrees. A 1½ HP router or larger is required and the router collet can be either 3/8 or ½. One-half inch is preferable. A Pro Clamp Kit is available at extra cost for production work and is especially useful for making drawers.
If you want large dovetails in thicker stock, you might want to consider Kellers Model 3600 Dovetail Jig. These 36 wide dovetail templates will handle thicknesses from ½ to 1 ¼ thick. The standard dovetail bit set works with wood up to 1 thick. The optional small dovetail bit set is for wood thicknesses from ½ to ¾. The optional large dovetail bit set is for stock 7/8 to 1¼ thick.