Dovetail jig
Also called: router dovetail jig, leigh jig
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A dovetail jig is a guide that clamps to a router and to the workpiece, letting the router cut dovetail joints, rows of angled pins and sockets called tails that interlock and resist being pulled apart, without the joint being marked and cut by hand.
What it cuts
A typical dovetail jig cuts a half-blind dovetail, a joint that shows on one face only, forming the pins and tails together in a single pass with one bit, and can cut dovetails across two different stock thicknesses. Paired with a router, a dovetail jig, whether bought or shop-made, can also cut slots for hidden splines, loose strips let into matching grooves to reinforce a joint.
Makes and variations
The Keller jig relies on a template guided by bearing-guided router bits, bits fitted with a small wheel that rides along the template's edge, and can also cut finger joints, straight interlocking fingers rather than angled dovetails, using an offset trimming bit. The Leigh jig instead pairs one finger template with several different dovetail cutter bits. At least one shop-built design departs from the usual layout by clamping directly onto the router's base rather than a separate fence.
When to use one
Router-cut dovetails made with a jig suit high-volume work, or jobs that do not need the extra strength of a hand-cut joint.