Cogged joint
Also called: cogging, cog joint, corking
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A cogged joint connects two timbers by cutting a projecting tooth, or cog, on one and a matching slot in the other so they partly sink into each other.
How it fits
The bearing piece carries the central cog or tenon, a projecting part of a joint, while the riding piece receives it in a chase, or cut slot. The two timbers then meet with less overlap than a plain crossing arrangement.
Where it is used
Cogged joints connect joists, the horizontal members that carry a floor, to binders, members that connect or support them. They are also used where a purlin, a roof member supporting rafters, rests on a principal rafter, or where joists bear on wall plates.
Allow for the cut
Cogging gives a timber a positive hold on its support, but cutting into a member removes some of its section. Lay out the tooth and slot so the remaining wood is adequate for the load, and do not deepen the recess simply to make assembly easier.